Summary

Door lock snapping is the fastest-growing method of forced entry to UK homes. A basic euro cylinder — even one marked 'anti-pick' — can be snapped in under 30 seconds using a long screwdriver and a kick. The weak point is the cylinder body, not the lock mechanism itself: once the front portion of the cylinder is broken off, the cam that operates the lock mechanism is exposed and can be turned with a screwdriver.

Anti-snap cylinders have a sacrificial snap point that causes the outer portion to break off before the inner working portion is reached. After snapping, the lock remains locked — entry is not gained. This is the single most cost-effective security upgrade for any external door with a euro cylinder.

Beyond cylinders, security hardware includes multipoint locking systems, hinge bolts, door chains and limiters, door reinforcement hardware, and letter box guards. This guide covers each element, relevant standards, and what to specify for different risk levels.

Key Facts

  • Euro cylinder (EN 1303) — standard in most uPVC and modern timber doors; 28–28mm to 35–35mm most common sizes
  • Anti-snap cylinder — sacrificial snap point breaks outer portion without defeating inner locking mechanism; required for all Part Q compliant doorsets
  • TS007 grading — 1-star to 3-star; 3-star = anti-snap + anti-pick + anti-drill + anti-bump; a 1-star door + 2-star cylinder = 3-star total per TS007:2014
  • BS 3621:2007+A2:2018 — five-lever mortice deadlock; standard for timber door deadlocks; key-operated from both sides or outside only with snib
  • BS 8621 — keyless egress version of BS 3621; key to lock from outside, knob/lever to exit from inside; required in HMOs for means of escape
  • Multipoint locking — 3-point to 7-point locking systems in uPVC and composite doors; hooks, rollers, and shoot bolts engage into the frame; significantly stronger than single-point locks
  • Thumb-turn cylinders — convenient (no key needed inside) but less secure; avoids key-trapped risks in fire but allows access through letterboxes; not recommended as sole cylinder type in vulnerable locations
  • Hinge side — outward-opening doors (rare in UK domestic but common for outbuildings): must have non-removable hinge pins or hinge bolts fitted; otherwise hinges can be driven out to gain entry
  • Door chain — allows partial opening without full unlock; useful for answering door to strangers but not a security measure for unoccupied properties
  • PAS 24:2022 — tests complete doorset system; replaces BS 7950 (now withdrawn)
  • Letterbox position — should be ≥400mm from any lock or handle; anti-fishing plate inside required for Part Q compliance

Quick Reference Table

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Hardware Standard Risk Reduction Cost Guide
Anti-snap cylinder (3-star) TS007 High — prevents cylinder snapping £20–£60
Five-lever deadlock BS 3621 High — solid timber doors £30–£80 + fitting
Multipoint lock (complete) PAS 24 Very high — three or more bolt points £80–£250 + fitting
Hinge bolts (pair) — Medium — prevents hinge-side attack £10–£20 + fitting
Door reinforcement kit — Medium — strengthens weak letterbox/lock areas £50–£150
Letterbox guard (cage) — Medium — prevents letter/hook fishing £15–£40 + fitting
Door viewer/spy-hole — Low-medium — allows identification of callers £5–£15 + fitting

Detailed Guidance

Identifying the Right Cylinder

Before upgrading a cylinder, measure correctly:

  1. Open the door and measure from the edge of the door to the centre of the cylinder (outside measurement = 'OA', inside measurement = 'OB')
  2. Standard euro cylinder designation: OA × OB (e.g. 35/35 = 35mm both sides)
  3. A cylinder that is too long protrudes and is easier to grip for snapping
  4. The ideal fit: cylinder should be flush with (or 1–2mm recessed into) the outer door furniture when fitted

Look for TS007 3-star rated cylinders or equivalent. Brands include:

  • Brisant Secure (ULTION — TS007 3-star)
  • ERA Invincible (TS007 3-star)
  • Yale Platinum (TS007 3-star)
  • ABS Locks (anti-snap certified)

For uPVC doors, matching the cylinder length to the existing multipoint lock is important — measure the existing cylinder before ordering a replacement.

Multipoint Lock Systems

uPVC and composite doors almost universally use multipoint locking systems operated by a handle (upward lift engages all bolt points) or by an internal handle with a key cylinder for external locking. The lock body typically contains:

  • Main latch (spring bolt for casual closing)
  • 2–4 hook bolts (engage into steel keeps in the frame)
  • 1–2 roller/shoot bolts (vertical engagement top and bottom)

The hook bolts in a multipoint lock are very strong — they are near-impossible to force. The weakness is the cylinder. With an anti-snap cylinder, a uPVC door with a quality multipoint lock is genuinely difficult to breach without significant noise and time.

Gearbox replacement: The gearbox is the mechanical heart of the multipoint lock. If the handle is loose, stiff, or the mechanism is worn, the gearbox can be replaced without replacing the entire door. Match by manufacturer and lockcase dimensions — common brands include Fuhr, Maco, Avocet, Winkhaus. Some are interchangeable; most are not.

Timber Door Mortice Locks

For traditional timber front doors with a single mortice lock:

  • Minimum BS 3621 five-lever deadlock
  • Check existing lock — many older timber doors have a two-lever or three-lever lock that provides almost no resistance to attack
  • Five-lever deadlock: 11mm minimum bolt throw, hardened steel anti-saw pins
  • For listed properties and period doors, slim-case versions available to fit in narrower stiles (min 44mm door thickness for standard case)

On many older timber doors, the door itself is the weak point — panels can be kicked in or frame can be split at the lock keep. Door reinforcement products (frame reinforcement bars, strike plate reinforcers with long screws into the structural stud/masonry behind) significantly improve performance even on older doors.

Door Chain and Door Bar

A door chain allows the door to be opened 50–100mm to speak to a caller without fully unlatching. Useful for elderly or vulnerable occupants. Install with long screws (minimum 50mm) into sound masonry or timber.

Door security bars (floor-mounted or top/bottom bolt bars) provide good resistance against forced entry but are inconvenient for regular use and create an egress problem in emergencies. Not recommended as a primary security measure.

Frequently Asked Questions

My client's uPVC door was forced by cylinder snapping — what do I install?

Fit a TS007 3-star anti-snap cylinder (sized to match existing). Confirm the multipoint lock gearbox and hook bolts are undamaged — cylinder snapping sometimes damages the lock cam mechanism. While you are there, check the frame strike keeps are properly fixed and the door sits squarely in the frame (a misaligned door puts stress on the bolts and makes them harder to engage). Total cost including a quality cylinder and adjustment: £60–£120.

My client has a letterbox in the middle of the door and a thumb-turn cylinder — should I move it?

The letterbox should be ≥400mm from the lock and handle. If the letterbox is positioned next to the lock, install an anti-fishing cage on the inside (a metal plate that deflects anything passed through the letterbox away from the lock mechanism) — this is far less disruptive than moving the letterbox. Replace the thumb-turn with a key cylinder if possible, or fit a letter-cage behind the box, or a sashlock rather than deadbolt so that reaching through cannot turn the thumb-turn from outside.

Does BS 3621 compliance mean my client is insured?

Insurance requirements vary by policy. Most standard contents policies require 'a lock conforming to BS 3621' or 'a five-lever deadlock' on wooden front and back doors. However, the policy wording varies — some policies require BS 3621 compliance on all external doors including patio and back doors. Read the policy before specifying locks on renovation work to avoid the client having claims rejected.

Regulations & Standards

  • PAS 24:2022 — Enhanced security performance requirements for doorsets (complete system)

  • BS 3621:2007+A2:2018 — Thief resistant lock assemblies: key egress (five-lever deadlock)

  • BS 8621:2007+A2:2018 — Keyless egress version (required in some HMO/means of escape situations)

  • TS007:2014 — Cylinder security rating scheme (1, 2, and 3-star)

  • EN 1303:2015 — Building hardware: cylinders for locks (general cylinder standard)

  • Approved Document Q (2015 + 2022) — security requirements for new dwellings

  • Secured by Design — Products List — certified products for Part Q compliance

  • Master Locksmiths Association — guidance on lock standards and cylinder security

  • Brisant Secure — Anti-Snap Guide — clear explanation of cylinder snapping and anti-snap technology

  • part q security — Part Q requirements for new dwellings

  • window types — window security and PAS 24 for windows

  • alarm systems — complementary intruder alarm systems

  • fire doors — where security and fire requirements interact