French doors have two weak spots a single door doesn’t: the centre where the two leaves meet, and the second (fixed) leaf that’s only held by bolts. The most effective French door security devices tackle those points first: a 3-star anti-snap cylinder, strong top and bottom bolts on the fixed leaf, a lock that ties the handles together, plus hinge bolts and laminated glass where needed.
Below are seven devices worth considering, what each one fixes, and what to check before you buy. We’ll also be clear about what doesn’t suit French doors, including our own products.
Why French doors need extra attention
A set of French doors has an active leaf (the one with the handle and key) and a secondary leaf (sometimes called the slave or passive leaf). The secondary leaf is usually held by bolts into the head of the frame and the threshold. If those bolts are short, worn or left undone, both doors can be pushed open together, however good the main lock is.
French doors also tend to have a lot of glass, and if they open outwards the hinges can be exposed. So you’re looking at four areas: the lock, the secondary leaf, the hinges and the glazing.
Quick comparison
| Device | What it fixes | Drilling needed? |
|---|---|---|
| 3-star anti-snap cylinder | Lock snapping and other cylinder attacks | No (direct swap) |
| Shoot bolts / rack bolts on the secondary leaf | Both doors being forced open together | Usually, unless upgrading existing bolts |
| Handle-locking device | Handles being turned after a lock attack | Varies by product |
| Lockable sash jammers | Extra locking points | Yes (screw-fixed) |
| Hinge bolts | Doors being levered off the hinge side | Yes |
| Laminated glass or security film | Glass being broken through | No (but glazing work for laminated) |
| PAS 24 replacement doorset | All of the above, tested as a unit | Full installation |
1. A 3-star anti-snap euro cylinder
Most uPVC, composite and aluminium French doors use a euro cylinder to work the multipoint lock on the active leaf. Basic cylinders can be snapped, so this is usually the first thing to upgrade. Our guide to anti lock snapping explains the risk in more detail.
What to look for: a cylinder rated TS 007 3-star or Sold Secure SS312 Diamond. West Yorkshire Police say a 3-star solution is the minimum to aim for when upgrading, and that cylinders should be measured properly and not left protruding from the door or handle.
Before you buy: measure from the central fixing screw to each end of your current cylinder, and check the rating applies to the size you need.
2. Shoot bolts or rack bolts on the secondary leaf
This is the step most often overlooked. On uPVC and aluminium French doors, the secondary leaf usually has shoot bolts operated by a small lever or handle on the door edge, sending bolts up into the frame head and down into the threshold. On timber doors, West Yorkshire Police recommend fitting mortice rack bolts to the top and bottom of each door leaf.
What to check:
- Do the bolts actually reach and engage the keeps when thrown?
- Are the keeps fixed firmly, or has the threshold or frame worn around them?
- Do you throw them every time, not just when you go on holiday?
If the shoot bolt mechanism is worn, a locksmith or door specialist can usually replace it with a matching unit for your door system.
3. A handle-locking device
Some products lock the two handles of a French door together so neither can be turned. One real 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 door mechanism can’t be operated even if the locks are snapped or removed. It’s sold through the Neighbourhood Watch shop, with part of each sale going to its community grants scheme.
What to check: that your handle style and spacing are compatible, and how the product is removed in a hurry. Look at the manufacturer’s fitting guide before you buy.
This is the type of device to consider for French doors rather than a floor-braced door bar designed for single doors.
4. Lockable sash jammers
A sash jammer is a small surface-mounted device screwed to the door or frame. When engaged, a lever or cam blocks the door from opening. Lockable versions need a key to release, which matters on glazed doors because a non-locking jammer could be flipped open by someone reaching through broken glass.
What to check:
- That the jammer suits your door material and profile.
- That the screws will bite into something solid, not just a thin plastic skin.
- That fitting won’t affect any warranty on the doors.
Because they need screwing in, sash jammers aren’t usually an option for renters without the landlord’s permission.
5. Hinge bolts or hinge protectors
If your French doors open outwards, the hinges are on the outside. Hinge bolts are steel pins fitted to the hinge edge of each door that locate into the frame when the door is shut, so the door stays in place on that side even if the hinges are attacked. West Yorkshire Police advise fitting hinge protectors or hinge bolts to each door hinge on French doors.
What to check: whether your doors open in or out, and whether the door edge is deep enough to take the bolt. Many modern uPVC French doors already have hinge-side security built in, so check before adding more.
6. Laminated glass or security film
French doors are often mostly glass. Laminated glass has a plastic interlayer that holds the pane together when it cracks, making it slower and noisier to break through. West Yorkshire Police suggest laminated security glass to BS EN 356 P1A or greater for vulnerable doors, and Avon and Somerset Police note that glass can be strengthened with security film or laminated panels.
What to check:
- For laminated glass, ask your glazier which BS EN 356 class they’re offering.
- For film, use a product sold as security film (not decorative film) and have it fitted properly.
- Check the beading and seals. West Yorkshire Police warn that old, split putty or bonding makes glass easier to remove.
7. A PAS 24 certified replacement doorset
If your French doors are old, warped or don’t lock properly, upgrading parts may cost more than it saves. Avon and Somerset Police advise using a security-accredited product to a standard such as PAS 24:2022 when replacing a door, and West Yorkshire Police recommend buying a complete doorset certified to PAS 24. That means the frame, leaves, locks, hinges and glass have been tested together, not just the lock.
What to check: ask the supplier for the certification for the exact doorset you’re buying, and make sure the installer fits it as tested.
What about door security bars?
Floor-braced door bars, including the HOLDOOR Door Jammer, are designed for single doors with one handle. They aren’t suitable for French or double doors, because the two leaves meet in the middle and bracing one leaf doesn’t hold the pair together. For French doors, stick to the devices above. If your concern is a sliding patio door, look for anti-lift blocks and a bar or lock made for sliding tracks.
FAQs
What is the weakest point on French doors?
Often it’s the secondary leaf. If its top and bottom bolts are weak or not engaged, both doors can be forced together. The cylinder on the active leaf is the other common target.
Can I secure French doors without drilling?
Partly. Swapping the cylinder needs no drilling, and some handle-locking devices fit without tools. Bolts, hinge bolts and sash jammers usually need screws. Our renter’s guide covers other no-drill options.
Are French doors less secure than a single door?
Not necessarily. A modern PAS 24 French doorset with a 3-star cylinder can be very secure. Older sets with worn bolts and basic cylinders are where problems usually arise.
Do I need a locksmith?
For a cylinder swap, many people do it themselves. For shoot bolt mechanisms, hinge bolts or rack bolts, a locksmith or door specialist will make sure they’re fitted to work as intended.
Next steps
- Check the cylinder on your active leaf for a TS 007 3-star or SS312 Diamond mark.
- Throw the secondary leaf’s bolts and check they engage firmly at top and bottom.
- Look at the hinges and glazing, and plan upgrades where needed.
- Then look at your other doors. If you also have a single uPVC back door, the Door Jammer – HOLDOOR hooks under its inside handle and braces it against the floor, so it stays shut even if the lock is snapped, bumped or picked. It’s Sold Secure Bronze rated, Secured by Design accredited (Police Preferred Specification), and fits most UK single-handle uPVC doors without drilling. See our guide to securing your home for a whole-house checklist.
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.
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