Double Door Security Bars: 6 Heavy-Duty Door Security Options

by iain macLEOD | Oct 31, 2026 | Home Security

A double door security bar works by tying both leaves together or bracing them against something solid, so the doors can’t be pushed apart at the centre where they meet. The right option depends on the doors: a cross bar or padbar for sheds and garages, strong top and bottom bolts plus a handle lock for French doors, and a track bar or anti-lift blocks for sliding patio doors. Floor-braced bars made for single doors aren’t the answer for a pair.

Here are six heavy-duty door security options for double doors, what each one is good for, and what to check before buying.

Why double doors are harder to secure

A pair of doors usually has one active leaf with the lock and one secondary leaf held by bolts at the top and bottom. The two meet in the middle with no fixed frame between them. That means:

• If the secondary leaf’s bolts are weak, both doors can be forced together.
• A bar or brace on just one leaf doesn’t hold the pair.
• On outward-opening doors, the hinges may be exposed.

So good double door security is about the centre join, the bolts and the hinges, not just the lock.

Options at a glance

1. A cross bar with fixed brackets

This is the traditional heavy-duty approach. Strong brackets are fixed either side of the doors and a steel bar drops in across both leaves on the inside. With the bar in place, neither door can be pushed open at the centre.

Good for: shed, garage and outbuilding doors, or a pair of house doors you rarely use.

What to check:

• The brackets are only as strong as their fixings. They should go into solid timber, the structural frame or masonry, not thin cladding.
• The bar should be long enough to span both leaves and sit well inside each bracket.
• Think about access. A cross bar has to be fitted from inside, so it suits doors with another way in and out.

2. A padlockable locking bar or padbar

For sheds and garages that are locked from outside, a locking bar or padbar spans the join and is secured with a padlock. Specialist retailer Insight Security lists a heavy-duty hasp and locking bar rated Sold Secure Silver, and its shed security advice suggests bolstering shed security with a door security bar.

What to check:

• Look for an independent rating such as Sold Secure on the bar or hasp, and use a padlock of a similar grade. A strong bar with a weak padlock is only as good as the padlock.
• Make sure the fixings are covered when the bar is locked, so they can’t simply be unscrewed.
• Check the hinges too. Insight’s advice is to make sure all door hinges are robust.

3. A handle-locking device for French doors

On French doors with lever handles, some devices hold the handles in place so neither door can be opened. One example is the Patlock, which Neighbourhood Watch describes as an instant French door security lock that works by holding the door handles in place, so the mechanism can’t be operated even if the locks are snapped or removed.

What to check: that it suits your handle style and spacing, and that you know how to remove it quickly from inside.

4. Strong bolts on the secondary leaf

Often the best “bar” for house double doors is already there: the bolts on the secondary leaf. On uPVC and aluminium doors these are usually shoot bolts operated from the door edge. On timber French doors, West Yorkshire Police recommend mortice rack bolts at the top and bottom of each door leaf, plus hinge protectors or hinge bolts on each hinge.

What to check: that the bolts engage fully at the top and bottom, the keeps are firm, and you actually throw them every time. Pair this with a TS 007 3-star or Sold Secure SS312 Diamond cylinder on the active leaf. West Yorkshire Police describe a 3-star solution as the minimum to aim for when upgrading.

5. A sliding door bar or anti-lift blocks

Sliding patio doors are often grouped with double doors, but they need different protection. A bar laid in the bottom track stops the sliding panel moving. To stop the door being lifted out, West Yorkshire Police note that a timber batten fixed into the top track of the frame can help, and suggest asking for anti-lift blocks and the sliding section to be on the inside when buying. Avon and Somerset Police also recommend anti-lift tracks for aluminium sliding doors.

What to check: that any track bar fits snugly for your door’s track width, and that anti-lift blocks are fitted by someone who knows your door system.

6. An alarmed bar or door contact alarm

Some door bars include a built-in alarm, and simple battery door contact alarms can be added to almost any door. These add a warning rather than strength, which can be useful for a garage or outbuilding you can’t see from the house.

What to check: what actually triggers the alarm, how loud it is according to the product details, and how you’ll know when the battery is low. Treat an alarm as an extra, not a replacement for a physical barrier.

A note on fire safety

If a pair of doors is a way out of your home, don’t secure it in a way that would stop you getting out quickly in an emergency. Keep keys for bars and padlocks somewhere everyone in the house knows about, and make sure at least one escape route is always easy to open from inside.

What about single back doors?

Many homes have French or patio doors at the back and a single uPVC back door as well. For that single door, a floor-braced bar is a strong extra layer. Our guide on whether a door security bar can stop a kick-in explains how they work, and our article on weak points of uPVC doors covers what else to check.

The Door Jammer – HOLDOOR hooks under the inside handle of a uPVC door and braces it against the floor, so the door stays shut even if the lock is snapped, bumped or picked. It’s Sold Secure Bronze rated and Secured by Design accredited (Police Preferred Specification), adjusts from 70cm to 120cm, and fits most UK single-handle uPVC doors with the handle on the left or right. There’s no drilling and no tools; it fits in about a minute. It’s not for sliding, French, double or patio doors.

In a fire: find the key, lift the Door Jammer off (or unlock and remove the Door Handle Guard), unlock the door and leave the building.

FAQs

Can I use a normal door security bar on French doors?

Floor-braced bars made for single doors aren’t designed for French doors, because the two leaves meet in the middle and bracing one leaf doesn’t hold the pair. Use secondary leaf bolts and a handle-locking device instead.

What’s the most secure way to lock double shed doors?

A cross bar on the inside, or a padlockable locking bar on the outside, fixed into solid timber and used with a padlock of a similar grade. Look for independent ratings such as Sold Secure where available.

Do I need to drill to fit a double door security bar?

Usually, yes. Cross bars, locking bars and bolts all need fixings. If you’re renting, see our renter’s guide to securing a door without drilling and check with your landlord.

Are alarmed door bars worth it?

They can be a useful extra warning, especially for outbuildings. They’re not a substitute for strong bolts, a rated lock and a solid bar.

Next steps

1. Identify your door type: shed or garage, French doors, or sliding patio doors.
2. For house double doors, check the secondary leaf bolts and the cylinder rating first.
3. For outbuildings, choose a properly fixed cross bar or rated locking bar with a matching padlock.
4. For your single uPVC back door, add the Door Jammer – HOLDOOR. It’s made in Britain from British steel and costs £90 with free UK delivery, 30-day returns and a 2-year warranty.

Home Security Alarm Systems UK: Types Compared and What to Look For

by iain macLEOD | Oct 31, 2026 | Home Security

The best home security alarm system in the UK depends on who you want to respond when it goes off. A simple audible alarm scares off intruders and alerts neighbours; a smart DIY system sends alerts to your phone; a professionally monitored system has an alarm receiving centre check every alert and call keyholders or, if the system qualifies, the police. This guide compares those types, explains the standards and accreditations that matter, and gives a checklist for choosing, so you can judge any brand on its merits rather than its advertising.

One principle comes before all of them. Avon and Somerset Police advise: “Sort out your physical security first and put the alarm in afterwards.” An alarm tells you a break-in is happening; good doors and locks help stop it.

The main types of home alarm system

1. Audible-only (bells-only) alarms

When triggered, the alarm sounds a loud siren designed to scare off an intruder and alert neighbours. There is no monitoring, so it relies on someone hearing it and acting. Police are less likely to respond to an unmonitored alarm.

Good for: deterrence on a budget, homes where neighbours are close by.

2. Smart DIY alarms (self-monitored)

Wireless kits with a hub, door and window contacts, motion sensors and a siren, controlled by an app. When the alarm triggers you get a phone notification and decide what to do. Many offer optional paid plans with extra features or professional monitoring. They are quick to fit, easy to expand and can move house with you, which suits renters.

Good for: renters, smaller homes, people who are comfortable reacting to alerts themselves.

3. Auto-dialler alarms

The system automatically calls or texts stored phone numbers when triggered. Avon and Somerset Police warn not to programme 999 into an auto-dialler, because police are unlikely to respond to automated calls. Put trusted keyholders’ numbers in instead.

Good for: people who want alerts without a monitoring contract, with reliable keyholders nearby.

4. Professionally monitored alarms (keyholder response)

Signals go to an Alarm Receiving Centre (ARC), staffed around the clock, which checks whether an alert is genuine and contacts you or your keyholders. These are usually installed by the provider and come with a monthly fee and a contract.

Good for: people who travel, live alone, or cannot always respond to a phone alert.

5. Monitored alarms with police response

The top tier. Crimestoppers explains that police attend a monitored alarm signal only if the system complies with the National Police Chiefs’ Council (NPCC) Security Systems Requirements; for a non-compliant system the keyholder is informed instead. A compliant system needs an installer approved by one of the two inspectorates, NSI or SSAIB, and registration with your police force, which issues a Unique Reference Number (URN). The NSI notes that police response is withdrawn after three false alarm calls in a rolling twelve-month period, so a reliable, well-maintained system matters.

Good for: higher-value homes, or where your insurer asks for it.

Alarm types compared

Costs vary widely between providers, so get written quotes that show equipment, installation, monthly fees, contract length and cancellation terms side by side.

What to look for in any alarm system

A recognised grade

Professional intruder alarms are graded 1 to 4 under the European standard EN 50131. Grade 2, designed to resist intruders with some knowledge of alarms, is the usual grade for homes; grades 3 and 4 are for commercial and high-risk premises. Many DIY smart kits are not graded at all. That does not make them useless, but it is worth knowing, especially if your insurer asks.

An accredited installer

For professionally installed systems, check that the company is approved by NSI or SSAIB. Crimestoppers advises checking installers on the inspectorates’ own websites.

Visible external sounders

Police advice is that two visible alarm boxes are better than one: mount them at the front and rear, high up to resist tampering. Signage helps too, but only with an active system behind it.

The right sensors in the right places

• Door contacts on every external door, including the back door and any door from an integral garage.
• Motion sensors covering the hallway and main routes through the house. Pet-tolerant sensors reduce false alarms if you have animals.
• Window contacts on easily reached windows.
• Coverage for any extension. Police specifically remind people to extend their alarm when they extend the house.
• Optional sensors on sheds and garages if they are in wireless range.

Reliability

Look for battery backup for the hub and siren, low-battery warnings, tamper alerts and, for app-based systems, a mobile data backup if your broadband drops. False alarms annoy neighbours and, on police-response systems, can cost you that response.

App and account security

For smart systems, use a strong unique password and turn on two-factor authentication if it is offered. Check who can arm and disarm the system and remove old users.

Contract terms

Read the minimum term, what happens if you move, who owns the equipment and the cost of leaving early. Some providers lease the equipment, so it goes back when you cancel.

Adding cameras and doorbells

Many alarm systems integrate cameras and video doorbells. If a camera records beyond your property boundary, the Information Commissioner’s Office says data protection law applies: aim cameras at your own property where possible, display a sign saying CCTV is in use, delete footage regularly and respond to requests for footage from people you record. Lighting helps too; police suggest dusk-till-dawn lighting as an alternative to motion-sensor lights that animals and visitors can set off.

Physical security: the part an alarm cannot do

An alarm reacts after someone tries to get in. Strong doors and locks make that harder in the first place, and they matter most when you are at home and the alarm may not be set downstairs. Start with:

1. A rated euro cylinder (TS 007 3-star or Sold Secure Diamond). Our guide to anti lock snapping explains what to look for.
2. Locking uPVC doors properly: lift the handle and turn the key every time.
3. A door security bar or handle guard for when you are in.
4. Window locks on accessible windows.

For a full plan, see our guide on how to secure your home.

Which alarm is right for you?

• Renting or on a tight budget: a smart DIY kit, plus a physical door device that needs no drilling. Our renters’ guide to securing a door without drilling covers options.
• Homeowner who wants alerts but no contract: a smart DIY kit with external siren, or an auto-dialler with good keyholders.
• Away often, live alone or vulnerable: a professionally monitored system.
• Insurer requires it, or higher-value home: a police-response system from an NSI or SSAIB approved installer. Ask your insurer exactly what they need before buying.

FAQs

Will the police respond to my burglar alarm?

Only if it is a monitored system that complies with the NPCC Security Systems Requirements, installed by an approved company and registered with your force. Police are less likely to respond to unmonitored alarms and are unlikely to respond to automated 999 calls.

Are DIY smart alarms any good?

They can be a sensible choice, especially for renters and smaller homes. The trade-off is that you have to respond to alerts yourself unless you pay for monitoring, and many are not graded under EN 50131.

What does NSI or SSAIB approval mean?

They are the two independent inspectorates for UK security companies. An approved installer is regularly inspected and can install systems that meet the standards police and insurers require.

Does a burglar alarm lower home insurance?

Some insurers offer a discount or require a particular type of alarm, but terms vary. Ask your insurer before you buy, and make sure you set the alarm as your policy requires.

Next steps

Whichever alarm you choose, make the doors hard to open first. For uPVC doors, the Door Jammer – HOLDOOR hooks under the inside handle and braces the door against the floor, so it stays shut even if the lock is snapped, bumped or picked. It is Sold Secure Bronze rated and Secured by Design accredited, fits most UK single-handle uPVC doors in about a minute with no drilling, and is made in Britain from British steel. It is £90 with free UK delivery and a 2-year warranty. It is not for sliding, French/double or patio doors; for those, look for a product designed for that door type.

In a fire: find the key, lift the Door Jammer off (or unlock and remove the Door Handle Guard), unlock the door and leave the building.

What Are uPVC Door Locking Mechanism Parts? A UK Guide

by iain macLEOD | Oct 31, 2026 | Home Security

A uPVC door locking mechanism is the long metal strip on the edge of the door that throws hooks, bolts or rollers into the frame when you lift the handle. Its main parts are the euro cylinder (where the key goes), the centre gearbox (which drives everything), the multipoint strip and faceplate, the keeps on the frame, and the handles and spindle. When something fails, you can usually replace that one part rather than the whole door.

This guide explains what each part does, how to work out which one has failed, the measurements you need before ordering a uPVC door lock mechanism replacement, and how to choose parts that improve security rather than just restore it.

How a uPVC multipoint lock works

When you lift the handle, the gearbox in the middle of the door converts that movement into a coordinated throw of several locking points along the strip. Each one engages a keep fixed to the frame. Turning the key in the cylinder then deadlocks the mechanism, so the handle cannot simply be pushed back down.

Spreading the locking across several points makes the door harder to force and pulls it tight against its seals. The catch is alignment. If the door has dropped or the keeps have moved, you will feel the handle getting stiff, and that extra friction wears out the gearbox. Most “broken lock” call-outs start with a door that has been slightly out of line for months.

The main parts, explained

The centre gearbox

The gearbox takes most of the strain, which is why it is one of the most commonly replaced parts. To identify a replacement, note any brand name or code stamped on the faceplate, then measure the backset and PZ (see below), the case height and depth, and the position of the fixing screws. Specialist suppliers such as Lock Shop Direct warn not to order on brand or backset alone, because many gearboxes look similar.

Locking points

• Hooks grab the keep and resist the door being levered or lifted.
• Deadbolts and pin bolts are straight throws that add rigidity.
• Rollers and mushroom cams pull the door into its seals; some designs also resist lifting.

Euro cylinder

The cylinder is the easiest part to change and the most important security upgrade. Police forces recommend a cylinder rated TS 007 3 star, or a 1 star cylinder combined with 2 star security handles, according to West Yorkshire Police. Cylinders tested to Sold Secure SS312 Diamond are also tested to a high standard, and some carry both ratings. TS 007 testing covers attacks including snapping, drilling, picking and bumping, as explained in this TS 007 guide.

When measuring, take the retaining screw out and measure from the screw hole to each end of the cylinder separately; many cylinders are offset. The outside end should sit close to flush with the handle. West Yorkshire Police’s door and window advice says it should not protrude more than 3mm beyond the door furniture.

Handles and spindle

A single spindle is one square bar running through both handles, so either handle opens the door. A split spindle is in two halves: the outside lever lifts to lock but will not open the door, so you need the key to get in from outside. A lever/pad set has a fixed pad outside and works the same way from outside, as this single vs split spindle guide explains. Before switching to a split spindle or lever/pad set, check that turning the key withdraws the latch on your lock; if it does not, you could lock yourself out.

Most uPVC handles use an 8mm square spindle, but measure yours to confirm. A worn, rounded spindle can make a handle feel loose and imprecise, and is a cheap part to replace. Sprung handles help if the gearbox’s own springs are tired and the lever droops.

The measurements you must get right

Work with the door open, photograph each step and measure to centres, not edges.

• Backset: from the front of the faceplate to the centre of the cylinder or spindle.
• PZ (centres): from the centre of the spindle to the centre of the cylinder. According to Door Furniture Direct, 92mm is the most common on modern multipoint locks, 68mm is often found on older doors and 70mm is less common.
• Handle screw centres: centre of the top fixing screw to centre of the bottom one, so the new handles cover the old holes.
• Gearbox size: case height and depth, and the fixing screw positions.
• Faceplate: width, profile (flat or U-rail), end shape and fixing-hole positions.
• Strip length and point positions: essential if you are replacing the full mechanism.
• Spindle: size and whether it is single or split.
• Cylinder length: from the retaining screw to each end.

Gearbox only, or the full mechanism?

Replace just the gearbox when the strip moves freely with the door open, the locking points are not worn, the faceplate is straight and you can find a matching gearbox. It is usually the quicker, less disruptive job.

Replace the full mechanism when several locking points are seized or worn, the faceplate is bent, the screw holes are chewed, or no matching gearbox is available. You may also need to adjust or replace the keeps so the new points line up.

Either way, fix the door’s alignment first. A new part fitted to a dropped door will start wearing straight away.

Quick diagnostics

Start with the door-open test: unlock the door, open it and lift the handle. If it is smooth when open but stiff when closed, the problem is alignment, not the lock. If it is stiff even when open, look at the gearbox or the strip.

• Floppy handle: take the handles off, put the spindle back in and turn it by hand. If the latch springs back firmly, the handle springs are tired, so fit sprung handles. If the latch feels lifeless, the gearbox springs have probably failed. Check the spindle for rounding too.
• Handle stiff only when the door is shut: look for rub marks on the hooks and keeps, then adjust the keeps or hinges in small steps.
• Key turns but nothing happens: with the door open, watch the bolt while turning the key. If nothing moves, the cylinder cam may not be engaging the gearbox, or the gearbox has failed internally. This is a good point to call a locksmith.

Maintenance that prevents failures

• Adjust the hinges so the locking points enter the keeps cleanly.
• Reposition keeps that show scraping marks.
• Lubricate the moving parts of the mechanism lightly, using a product the lock maker recommends, and keep grit out of the keeps.
• Tighten handle bolts, the cylinder retaining screw and hinge screws.
• Lift the handle fully before turning the key, and never force a stiff lock: find the cause instead.

Our guide to the top weak points of uPVC doors covers hinges, glazing and letterboxes as well as locks.

DIY or locksmith?

Swapping a cylinder or handles is a manageable DIY job for most people with a screwdriver and accurate measurements. Replacing a gearbox or full strip is more involved: you need the door wedged open, the latch taped back so it cannot click shut, and confidence that the replacement matches. If you are unsure, a Master Locksmiths Association member can identify, supply and fit the right parts, as West Yorkshire Police suggest. Ask for an itemised quote covering parts, labour and any adjustment.

When buying, choose suppliers that show full dimension drawings and will match your lock from photos and measurements.

Security upgrades while you are at it

• Cylinder: TS 007 3 star, or Sold Secure Diamond. See our anti-lock snapping guide.
• Handles: TS 007 2 star security handles, which can be paired with a 1 star cylinder.
• Spindle: the Security Spindle – HOLDOOR is an 8mm boxed steel spindle, 138mm long and trimmed to fit, with an anti-tamper security clip that resists handle manipulation. It is £14.00 with free UK delivery and is sourced from an overseas manufacturer.
• A second layer for when you are home: the Door Jammer – HOLDOOR hooks under the inside handle of a uPVC door and braces it against the floor, so the door stays shut even if the lock is snapped, bumped or picked. It is Sold Secure Bronze rated and Secured by Design accredited (Police Preferred Specification), adjusts from 70cm to 120cm for most UK single-handle uPVC doors (handle on the left or right), needs no drilling or tools and fits in about a minute. Made in Britain from British steel; invented and designed by Jon Gill in Manchester, with a wall mount; £90 with free UK delivery, 30-day returns and a 2-year warranty. It is not for sliding, French/double or patio doors.

Fire safety: In a fire: find the key, lift the Door Jammer off, unlock the door and leave the building.

FAQs

Can I replace a uPVC door lock mechanism myself?

Cylinders and handles, yes, for most people. Gearbox and full-strip replacement is possible DIY but needs careful measuring and patience; a locksmith is the safer choice if the door is your only exit or you are not confident.

How do I know which part has failed?

Use the door-open test. Stiff only when closed points to alignment; stiff when open points to the gearbox or strip; key turning with no effect points to the cylinder or gearbox.

Do I need to replace the whole door if the lock breaks?

Rarely. Most faults are fixed by a gearbox, cylinder, handle or spindle swap plus some adjustment.

What does PZ mean?

It is the distance between the centre of the handle spindle and the centre of the cylinder. Your handles and gearbox must match it.

Next steps

1. Do the door-open test to find out whether you have an alignment problem or a failed part.
2. Take the measurements above and photograph the faceplate before you order anything.
3. Upgrade the cylinder to TS 007 3 star (or Sold Secure Diamond) while the door is apart.
4. If your handle feels loose, consider the Security Spindle – HOLDOOR.
5. For an extra layer when you are home, see the Door Jammer – HOLDOOR.

uPVC Door Locking Mechanism: How It Works and How to Replace It

by iain macLEOD | Oct 31, 2026 | Home Security

A uPVC door locking mechanism is a multi-point lock: one long metal strip inside the edge of the door that throws several hooks, bolts or rollers into the frame at once, controlled by a gearbox behind the handle and the key cylinder. When it fails, the usual signs are a handle that will not lift, a floppy handle, or a key that will not lock the door. You can often fix the problem by adjusting the door rather than replacing the lock, but if the gearbox has failed, a careful DIYer can replace the mechanism with the right measurements and a couple of hours.

This guide explains how the mechanism works, how to tell whether it really needs replacing, how to measure for the right part and how to fit it, plus when to call a locksmith.

How a uPVC multi-point lock works

Most uPVC doors in the UK use the same basic layout:

• Gearbox (lock case): the central box behind the handles. It contains the latch, usually a deadbolt, and the gears that drive the rest of the lock.
• Faceplate and drive bar: the long metal strip you see on the edge of the door. Behind it, a sliding bar moves the locking points up and down.
• Locking points: hooks, mushroom cams, rollers or shoot bolts spaced along the faceplate that engage the frame.
• Keeps: the metal plates on the frame that the locking points engage.
• Euro cylinder: the key lock, which deadlocks the mechanism.
• Spindle and handles: the square bar through the gearbox that connects the inside and outside handles.

Lever-operated versus key-wind

On a lever-operated lock, lifting the handle throws the locking points and the key then deadlocks them. On a key-wind lock, the key itself throws the points, and on an automatic lock some or all of the points engage as the door closes. These types are not interchangeable, so check which you have: with the door open, lift the handle and see whether the hooks or bolts come out, then try the key. Some doors also use a split spindle, where the inside and outside handles work independently; that too must be matched like for like.

Diagnose before you buy anything

A lot of “broken locks” are really misaligned doors. If the door has dropped or the keeps are out of line, the locking points rub on the frame, the handle becomes stiff, and eventually the gearbox breaks under the strain. Replacing the mechanism without fixing the alignment just means the new one wears out too.

Quick tests

1. Open the door and operate the handle and key. If everything moves smoothly with the door open but is stiff when closed, the problem is alignment, not the lock.
2. Check the gaps. Look at the gap between door and frame on the lock side. If it is wider at the top than the bottom, the door has probably dropped. Adjusting the hinges usually fixes this; Everest’s hinge adjustment guide explains which screw does what.
3. Watch the locking points. If some move and others do not, the drive bar or a connection may have failed.
4. Feel the handle. A handle that drops loose, spins or will not return to horizontal, with the door open, usually points to a broken gearbox spring or gear.

Repair, adjust or replace?

If the door is locked shut and will not open at all, stop and call a locksmith. Forcing it can damage the door, frame and mechanism.

Measure for the right replacement

There are many mechanisms that look similar but do not interchange. Lock supplier Lockshop Direct’s multi-point lock measurement guide puts it bluntly: do not order from the brand or backset alone. Record the following:

• Brand and markings stamped on the faceplate or gearbox.
• Backset: from the front of the faceplate to the centre of the spindle or cylinder.
• PZ (centres): from the centre of the square spindle to the centre of the cylinder. Lock and Key notes that many uPVC handles are 92mm PZ, but always check yours.
• Gearbox height and depth.
• Faceplate: overall length, width, flat or U-rail profile, and square or rounded ends.
• Locking points: type and the distance from the spindle centre to the centre of each one, above and below.
• Operation: lever-operated or key-wind, single or split spindle, and whether the latch is reversible.

Photograph the whole mechanism once it is out, with a tape measure alongside. Suppliers can often identify a lock from good photos, and some doors only accept a replacement gearbox rather than a full strip.

Tools you will need

• Cross-head and flat screwdrivers (a long cross-head is useful for faceplate screws)
• Tape measure and pencil
• Your door key
• Silicone or PTFE spray lubricant
• A soft cloth or card to protect the door edge

Work during the day and plan to finish before night, because the door cannot be locked while the mechanism is out. Keep the door wedged open so it cannot swing shut on a half-fitted lock.

How to replace a uPVC door locking mechanism

These steps are for your own door with the key in hand and the door open throughout.

1. Remove the handles. Undo the screws on the inside handle plate, then take off both handles and slide out the spindle.
2. Remove the cylinder. Undo the cylinder retaining screw on the edge of the door, level with the cylinder. Insert the key, turn it slightly until the cam lines up with the cylinder body, and slide the cylinder out.
3. Remove the faceplate screws. There are usually screws along the full length. Keep them; you may need them if the new ones are a different length.
4. Ease the mechanism out. Pull the faceplate away from the door edge, working gently from the gearbox outwards. The strip is long, so ease it out without bending it or chipping the door.
5. Compare old and new. Lay them side by side and check the gearbox position, every locking point and the faceplate length before going further.
6. Fit the new mechanism. Slide it in, line up the gearbox with the handle and cylinder holes, and fit the faceplate screws loosely at first.
7. Refit cylinder, spindle and handles. Check the spindle turns the gearbox freely, then tighten everything without overtightening.
8. Test with the door open. Lift the handle, lock and unlock with the key, and operate both sides at least ten times before closing the door.
9. Test with the door closed. If the points rub or the handle is stiff, adjust the keeps on the frame or the hinges rather than forcing it.
10. Lubricate the locking points and keeps with a light spray.

Upgrade while the door is apart

Replacing the mechanism is a good time to improve the rest of the lock:

• Cylinder: West Yorkshire Police recommend a 3-star solution under TS 007 as the minimum when upgrading, or a cylinder to the Sold Secure Diamond Standard (SS312). See our guide to anti lock snapping.
• Handles: TS 007 2-star security handles add protection to the cylinder.
• Spindle: the Security Spindle – HOLDOOR is an 8mm boxed steel spindle, 138mm long and trimmed to fit, with an anti-tamper security clip that resists handle manipulation.

Make sure the cylinder is the right length; it should not stick out far from the handle.

Common problems after fitting

Handle stiff only when the door is closed

The locking points are catching on the keeps. Adjust the keeps or the door hinges until they engage cleanly. Home improvement firm Everest’s hinge adjustment guide explains the screws to use.

Key hard to turn

Check the handle is fully lifted first. If it is, the cylinder may be slightly out of line with the gearbox or the wrong length. Loosen and re-tighten the retaining screw with the cylinder centred.

Door has dropped again

Fix the hinges. A dropped door will damage any new mechanism eventually.

When to call a locksmith

Call a professional if the door is stuck locked, you cannot identify the mechanism, the door is still under an installer’s warranty (DIY may void it), or the door edge is damaged. West Yorkshire Police suggest a locksmith from the Master Locksmiths Association for advice and fitting. Costs vary widely with the lock and your area, so ask for a fixed quote that includes parts.

FAQs

Can I replace just the gearbox?

Often, yes. Many mechanisms allow the centre gearbox to be swapped on its own. You still need to match the brand, backset, PZ and dimensions exactly.

Why does my uPVC door handle have to be lifted to lock?

On a lever-operated lock, lifting the handle throws the hooks and bolts. Turning the key then deadlocks them. If you only turn the key without lifting the handle, the door is not fully locked.

Are all uPVC locking mechanisms the same?

No. Faceplate length and profile, backset, PZ, locking point positions and operation all vary. Measure everything before ordering.

Will a new mechanism stop lock snapping?

Not on its own. Snapping attacks the cylinder, so upgrade it to a rated cylinder. Read more about the weak points of uPVC doors.

Next steps

Once the lock is working and the door is aligned, add a layer that does not depend on the lock at all. The Door Jammer – HOLDOOR hooks under the inside handle of a uPVC door and braces it against the floor, so the door stays shut even if the lock is snapped, bumped or picked. It is Sold Secure Bronze rated, Secured by Design accredited, fits in about a minute with no drilling, and suits most UK single-handle uPVC doors (not sliding, French/double or patio doors). It is £90 with free UK delivery and a 2-year warranty.

In a fire: find the key, lift the Door Jammer off (or unlock and remove the Door Handle Guard), unlock the door and leave the building.

15 Types of Door Locking Mechanism Explained for UK Homes

by iain macLEOD | Oct 31, 2026 | Home Security

A door locking mechanism is the part of a lock that moves a bolt, latch or hook into the frame so the door can’t be opened. Most UK homes use one of three: a euro cylinder driving a multi-point lock (uPVC and composite doors), a mortice lock (timber doors), or a rim nightlatch (often paired with a mortice lock). Knowing which you have tells you which standard to look for and where the weak spots are.

This guide explains 15 common types of door locking mechanism found in UK homes, how each works, where it’s used and what to check.

The standards that matter

Before the individual locks, here are the UK standards you’ll see stamped on faceplates and packaging. They’re the quickest way to tell a good lock from a basic one.

Locks for uPVC and composite doors

1. Euro cylinder

The euro profile cylinder is the keyhole part on most uPVC and composite doors. Turning the key rotates a cam in the middle of the cylinder, which works the lock mechanism inside the door. It’s held in place by a single fixing screw through the edge of the door.

Older or basic cylinders can be vulnerable to lock snapping, so the rating matters. West Yorkshire Police say a 3-star solution is the minimum to aim for when upgrading, and that cylinders must be measured correctly so they don’t stick out from the door or handle.

2. Thumb-turn cylinder

A thumb-turn cylinder has a key on the outside and a small knob on the inside, so you can lock and unlock from inside without hunting for a key. That’s convenient and helpful for a quick exit. The trade-off is that a thumb-turn near a letterbox or glass panel could be reached from outside, so pair it with a good letterbox guard and choose one with a proper 3-star or Diamond rating.

3. Multi-point lock

Behind the handle of most uPVC and composite doors is a multi-point lock: a long strip running down the edge of the door with a central gearbox. Lifting the handle throws hooks, rollers or bolts into keeps along the frame; turning the key then locks them in place. Because the door is held at several points, it’s much harder to lever open than a single-latch door.

The catch is habit. If you close the door without lifting the handle and turning the key, often only the latch is holding it. Problems such as a stiff handle usually come from the door dropping out of line, not a broken lock; our guide to the weak points of uPVC doors explains what to check.

Locks for timber doors

4. Mortice deadlock

A mortice deadlock sits inside a pocket cut into the edge of a timber door, so only the keyhole and faceplate are visible. Turning the key throws a solid bolt into the frame. There’s no latch and no handle operation; it simply locks and unlocks.

For external timber doors, look for one marked BS 3621. West Yorkshire Police recommend a 5-lever mortice lock tested to BS 3621 on wooden doors, and note that insurers often require it. Check your own policy wording.

5. Mortice sashlock

A sashlock combines a deadbolt and a sprung latch in one case. The latch is worked by the handles, so the door can be pushed shut and opened without a key during the day, and the key throws the deadbolt at night. It’s common on back doors with lever handles. The same BS 3621 marking applies if you want insurer-friendly security.

6. Rim nightlatch

Often called a “Yale-type” lock, the nightlatch is the box mounted on the inside face of the door with a cylinder on the outside. It latches automatically when the door closes. Basic versions can be slipped or opened by reaching through a letterbox, so for a front door choose a deadlocking nightlatch. Some nightlatches are made to BS 3621. On most timber front doors, a nightlatch works best paired with a mortice deadlock.

Electronic locks

7. Smart locks

Smart locks let you lock and unlock with a phone app, fob, code or fingerprint. On UK uPVC doors, many work with a compatible euro cylinder and the existing multi-point lock rather than replacing it. Points to check:

• The security rating of the cylinder or lock, ideally TS 007 3-star or Sold Secure Diamond where it uses a euro cylinder.
• What happens when the battery runs low, and whether there’s a key override.
• Whether it still needs you to lift the handle to engage the multi-point lock.
• App security and account settings, such as two-factor login.

8. Keypad and push-button locks

Code locks are common on side gates, utility rooms and communal doors. Mechanical versions need no batteries; electronic versions often add features like temporary codes. They’re handy where several people need access, but change the code regularly and check what security standard, if any, the lock has been tested to.

Locks for patio, French and bi-fold doors

9. Patio door hook lock

Sliding patio doors usually lock with hook-shaped bolts that swing up into keeps on the frame, so the sliding leaf can’t be pulled open. The hooks don’t stop a door being lifted out of an older frame, which is why the Met advise checking for an anti-lift device.

10. Shootbolts and espagnolette locks

French doors and bi-folds often use shootbolts: rods that shoot up into the head of the frame and down into the threshold when the handle is turned. On French doors the second leaf usually has its own shootbolts at top and bottom, and the main leaf locks into it. Make sure both leaves are fully engaged every time.

Bolts and secondary locks

11. Mortice rack bolt

A rack bolt is fitted inside a hole drilled into the edge of a timber door and operated with a splined key from the inside only. It adds a hidden extra locking point at the top or bottom of the door, useful on back doors and French doors.

12. Barrel and tower bolts

Surface-mounted bolts are simple sliding bolts screwed to the inside face of a door. They’re only as strong as their screws and the material behind them, so use long screws into solid timber. They’re useful extra security for doors you rarely use, not a main lock.

13. Hinge bolts

Hinge bolts are fixed steel pins in the hinge edge of the door that sit in holes in the frame when it’s closed. They help stop the hinge side being forced, which matters most on outward-opening doors where the hinge pins are outside. West Yorkshire Police suggest hinge bolts or security hinges for outward-opening doors and on each hinge of French doors.

14. Sash jammers

A sash jammer is a small lever-type lock screwed to the inside of a uPVC door or window frame that swings across the opening edge. It’s an inexpensive extra, but it needs screwing into the profile, so check your door warranty first, as West Yorkshire Police also advise.

15. Padlocks and hasps

For sheds, garages and gates, a hasp and padlock is often the main lock. The weak point is usually the hasp, not the padlock, so choose a hasp whose screws are hidden when closed, and look for a Sold Secure rating on the padlock. Sold Secure grades products Bronze, Silver, Gold or Diamond, from opportunist to dedicated attacks.

Beyond the lock: holding the door itself

Every mechanism above relies on the lock staying intact. A floor-braced door bar works differently: it holds the door shut even if the lock is attacked.

The Door Jammer – HOLDOOR hooks under the inside handle of a uPVC door and braces it against the floor, so the door stays shut even if the lock is snapped, bumped or picked. It is Sold Secure Bronze rated and Secured by Design accredited (Police Preferred Specification), adjusts from 70cm to 120cm to fit most UK single-handle uPVC doors with the handle on the left or right, and fits in about a minute with no drilling or tools. It’s made in Britain from British steel and is used from inside, when someone is at home. It isn’t for sliding, French, double or patio doors.

In a fire: find the key, lift the Door Jammer off (or unlock and remove the Door Handle Guard), unlock the door and leave the building.

Frequently asked questions

How do I know what lock I have?

Look at the door edge. A long faceplate with several bolts or hooks means a multi-point lock, usually worked by a euro cylinder. A shorter faceplate with a keyhole on a timber door is a mortice lock; check it for a BS 3621 mark. A box on the inside face of the door is a rim nightlatch.

Which lock do insurers want?

It depends on the policy. Many ask for BS 3621 mortice locks on timber doors and specific locks on uPVC doors. Read your policy wording rather than assuming.

What’s the most secure lock for a uPVC door?

A multi-point lock used properly, with a TS 007 3-star or Sold Secure Diamond cylinder fitted at the right length. Add a door bar for extra protection when you’re home.

Can I change a euro cylinder myself?

Often yes, if you measure carefully and buy the right size. If you’re unsure, police advice is to use a Master Locksmiths Association approved locksmith.

Next steps

1. Identify the locking mechanism on each external door.
2. Check the markings: BS 3621 on mortice locks, TS 007 3-star or SS312 Diamond on cylinders.
3. Upgrade anything unmarked, starting with your front and back doors.
4. For a single uPVC door, add the Door Jammer – HOLDOOR so the door stays shut even if the lock is attacked.