What locks do composite doors use (and which are most secure)?

"What lock does my composite door have?" usually has two answers — the mechanism in the door edge and the cylinder you put the key into. Knowing the difference, and the ratings to look for, is the key to a secure door.

Multi-point locks: the mechanism in the door

The main locking on a composite door is a multi-point lock — a long mechanism running inside the leading edge of the door. When you lift the handle, it engages several locking points along the door's height; turning the key then deadlocks them. The locking points can be hooks (which pull the door tightly into the frame and resist levering), deadbolts, rollers (which mainly compress the seals) or a combination, and a typical composite door locks at three or more points. Spreading the locking up and down the door is what gives it real strength: the door is held against the frame along its length, so it cannot be sprung open at a single point the way a door with one central deadlock can.

Multi-point locks vary in quality. Better mechanisms use hardened steel hooks and are themselves tested as part of a PAS 24 door set. The handle (or 'door furniture') that operates the mechanism also matters, because on many systems the handle protects the cylinder — security handles with built-in cylinder protection are part of how some doors achieve their anti-snap rating. The point to take away is that the multi-point mechanism provides the holding strength of the door, but it is operated through the cylinder, which is the part an attacker is most likely to target.

Cylinders and the anti-snap rating

The cylinder is the barrel the key turns. Composite doors use a euro-profile cylinder, a standardised shape that is easy to replace — which is good for changing a lock, but means a cheap cylinder can be swapped for the same vulnerable part. The dominant attack on this kind of lock is cylinder snapping: an ordinary euro cylinder can be gripped and snapped to expose the mechanism in seconds. The answer is an anti-snap cylinder, designed with sacrificial sections and reinforcement so that even if part snaps off, the lock stays secure.

The UK rating to look for is TS007, which grades cylinders and door hardware in stars. The recognised secure combinations are a 3-star cylinder on its own, or a 1-star cylinder paired with 2-star security handles — both add up to the full protection. A cylinder carrying the Kitemark for the relevant standard is another mark of quality. These cylinders resist not just snapping but also drilling, picking and bumping. Because the cylinder is replaceable, upgrading to an anti-snap one is also the single most cost-effective security improvement on an existing composite door that was fitted with a basic cylinder.

Indicative guidance; a 1-star cylinder with 2-star handles is also a recognised secure combination.

Putting it together: the most secure setup

The most secure composite door locking combines the two elements so each does its job. The multi-point mechanism — ideally with hardened hooks engaging the frame at three or more points — provides the strength that resists kicking and levering. The cylinder — a TS007 3-star anti-snap unit, or a 1-star cylinder with 2-star security handles — protects against the snapping attack that would otherwise bypass everything else. Where the door has glazing within reach of the lock, laminated glass closes off the option of breaking the glass to reach the handle from inside.

The strongest assurance that these parts work together is that the whole door set is tested to PAS 24, because that standard assesses the leaf, frame, multi-point lock and cylinder as a single assembly. When buying, ask the supplier to confirm the multi-point lock type, the cylinder's TS007 rating, and that the configuration is PAS 24 tested. On an existing door, the practical priorities are to check the cylinder is anti-snap (and upgrade it if not), and to make sure the door is adjusted so the hooks engage fully into the keeps — a multi-point lock only protects you when the points actually lock home.

Keeping the lock secure and working

A secure locking setup only stays secure if it keeps working, and composite door locks reward a little attention. The most common reason a multi-point lock becomes unreliable is stiffness — either the mechanism running dry, or the door drifting slightly out of alignment so the hooks no longer meet their keeps squarely. The fix is to lubricate the mechanism, cylinder and keeps a couple of times a year with a suitable light lubricant (a lock-specific product for the cylinder, silicone or PTFE for the hardware), and to adjust the door via its hinges if the hooks are catching the edges of the keeps rather than dropping in cleanly. The golden rule is never to force a stiff lock: yanking the handle or wrenching the key against a stiff mechanism is the classic way to break the gearbox or snap the spindle, which then needs a full mechanism replacement.

It is also worth knowing your upgrade options on an existing door. Because the euro cylinder is a standardised, replaceable part, swapping a basic cylinder for a TS007 3-star anti-snap one is a quick, low-cost improvement that addresses the single biggest vulnerability. Fitting security handles can add cylinder protection, and where the multi-point mechanism itself has failed it can be replaced by a competent locksmith or installer. Together these mean a composite door's security can usually be brought up to standard, or restored, without replacing the whole door — making the lock the most cost-effective place to focus both maintenance and any security upgrade.

Frequently asked questions

Sources & further reading

• Secured by Design — official police security initiative
• gov.uk — Building Regulations Approved Document Q (security)

Figures on this page are typical UK ranges drawn from published sources and depend on your specific door and opening. They are guidance, not a quotation.