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Locks and Lock Standards [Hardfacts]


The range of security locks available to prospective purchasers is very wide. As a result, to the non-expert choosing a suitable lock can be daunting prospect – especially with locks often looking similar, but in fact being very different in terms of their security, quality and general reliability.

This Hardfacts describes basic lock types and related British or European standards with which they may comply. ‘Hardfacts’ 3017: Door and Window Security provides some related general advice.

Lock Types
All locks consist of four main parts, the case, the key/locking mechanism, the lock bolt mechanism and its receiving recess. Taking each of these items in turn, the three basic forms of lock case are:

  •  Mortice Lock A lock case designed to be fitted within a door or window. Where a handle operated latch is incorporated, such locks are called ‘mortice sashlocks’.
  • Rim Lock A lock case designed to be fitted to the internal surface of a door or window. 
  • Padlock A lock designed to be removable and which has a shackle (lockbolt) that passes through a separate staple/hasp. Two types exist, open shackle and closed shackle padlocks. An open shackle type has a shackle that, when placed through the staple, would permit a bolt cutter to be used on the shackle, or space for a jemmy to be inserted to attack the shackle or staple. A closed shackle padlock does not permit such ready access, and is thus inherently more secure. Hardened steel lock cases, or plates within it, can hinder an attack by drilling.

Moving on to lock mechanisms, the two most common key/locking mechanisms are:

  • Lever Locks A lock where the key has a number of stepped notches along its ‘bit’ which, when the key is put tin the lock and first turned, engage with a set of levers within the lock case and lift them. When all the levers are correctly raised, the key can turn and operate the lockbolt.
  • Cylinder Locks A lock where the key has a number of ridges along its length which, when the key is inserted into the cylinder engage with sprung pins inside it. When all the pins are correctly raised the key can turn the cylinder to operate the lockbolt.
    Increasing the numbers of levers/pins in a lock allows for more key variations, thus making it harder for thieves to ‘pick’ the lock. 5 levers/pins is the usual minimum for a secure lock.

All locks have a lock bolt designed to move in and out of the lock case and engage in a suitable recess.  Use of hardened steels, or inserts within the bolt, can hinder attack by cutting. A 'deadlocking' lockbolt is one that when it is in the locked position cannot be pushed back into the lock case.

For all locks except padlocks, a lock bolt receiving recess will need to be created. For mortice locks this will be a recess in the door frame (or another door if securing double doors). To protect the edge of this recess from wear, it usually has metal 'flush striking plate' fitted; but ideally, to hinder attack on the bolt once engaged within it, should be fitted with a 'boxed striking plate', i.e. one with an integral steel box to receive the bolt.  For rim locks a suitable surface fixed metal housing receives the lockbolt.   

UK Lock Standards
The security of a lock cannot reliably be assessed by simply looking at it, so tests that simulate common attack methods and usage are required to help prove its security.

Various European (EN) lock standards exist, those adopted within the UK being given a BSEN prefix. Sometimes called ‘CEN‘ standards these EN Standards are particularly complicated, with compliant locks having an eleven digit code to indicate various product features, only the 7th digit in the sequence usually being used to indicate the security ‘Grade’.

The CEN standards require the code to be shown on the lock packaging, but not the lock itself; and don’t usually require testing against lock picking, sawing or an expert review. As a result of these perceived limitations/weaknesses, CEN standards are infrequently referred to in the UK; except perhaps for padlocks, where there is no comparable British standard.

Of the various UK test standards that can apply to locks, the one most commonly cited by UK insurers over the years has been BS 3621. A few years ago this standard was set to be withdrawn when the UK needed to adopt the European Standards for door locks (EN 12209 and EN 1303), but it was eventually retained by redrafting it to cross refer to a security level within the European Standards and because of a unique UK requirement for a General Vulnerability assessment (GVA) - a further review/testing against possible weaknesses, as determined by a panel of expert locksmiths who study the lock design.

x621 Series
BS 3621 has since evolved into a suite of similar standards known as the x621 Series, which relate to both single point mortice and cylinder rim locks (as BS 3621, 8621 and 10621) and multi-point locks (as PAS 3621, 8621 and 10621). Whether chosen in a BS or PAS version, the respective differences in use are as follows:

  • 3621 – key lockable from both sides of the door
  • 8621 – key lockable from outside only, emergency escape always possible from inside without using a key, means of a handle/latch/thumb turn, etc.
  • 10621 – As 8621, but from outside (if you are sure no one remains inside – beware trapping risk) the internal emergency release can be disabled.

Such locks are most commonly identified by their carrying the BSI ‘Kitemark’ on the lock face and packaging.

Note. Most BS 3621 rim locks have an internal lockable handle, which can be used as a daytime latch, but must always be locked out of use to maintain door security - especially if the door has a letter flap or glazing in or adjacent to it, as this should stop persons outside gaining access to the handle to release it.

Other UK standards include:

  • BSEN 12209 – This is a UK version of a European Standard for door locks. Numerous different combinations (Grades) of lockcase/lock mechanism and key security are available, plus related testing for attack resistance, force, durability, fire and safety. The x621 Series calls up Security Grade 7, Key Security B - the latter only for lever locks. If a cylinder is used reference is made instead to BSEN 1303.
  • BSEN 1303 – This is a UK version of a European Standard for lock cylinders. Various security levels against attack and for key security are available. The x621 Series calls up Key Security Grade 5, Attack Grade 2.
  • TS007 - This is a UK Standard developed to recognise and protect against the risk of ‘snapping attacks’ on door lock cylinders. Snapping attacks relate to a form of criminal attack whereby a protruding cylinder is gripped by a wrench, or similar tool, and twisted until it snaps in its narrow middle section. TS 007 cylinders with a 3 Star rating can resist such attacks on their own, but a 1 Star cylinder needs to be married up with a 2 Star surrounding door handle to give an overall 3 Star level of protection.(Note. Sold Secure have a similar test standard for stand alone cylinders called SS312 – Diamond rating). 
  • TS008 - A UK Standard for testing letter flaps for resistance to external access/manipulation of internal door lock mechanisms.
  • PAS 24 - Applies to manual attack testing of single leaf domestic doorsets and windows, including locks (but excluding picking/sawing) and hinges. Any glazing must be laminated if the door/window could be opened from inside without a key, and similarly any letter flap must defeat external manipulation of a door lock release.
  • BS 8607 - This is a UK Standard for mechanically operated push button locksets. A Grade 4 rating is intended to be comparable to a x621 series lock.
  • BSEN 12320 - This standard reflects a European Standard for padlocks and staples (padbars) of all types, i.e. open and closed shackle. Security Grades range from 1-6, 6 being the highest.
  • BSEN 179 & BSEN 1125 - These standards are UK versions of European Standards for emergency escape door mechanisms at premises where, respectively, no panic is likely to occur, e.g. a factory/office, and those where it might, e.g. a shop or club/pub. Where an external keylock is incorporated, it should be tested to a security level chosen from BS EN 12209 (for external attack only).

Lock Certification
Claims that a lock has been tested to a particular standard can only be relied upon where the test has been undertaken and ‘certified’ by a recognised independent test body, e.g. in the UK typically by the BSI (Kitemark scheme), the MLA (Sold Secure scheme) or the BRE (LPCB scheme).

Given the complexity of some standards, the omission from some of certain desirable security tests and the need to consider a lock alongsie the intended type of door/window, the MLA and LPCB operate their own lock security grading & testing schemes - which reflect and build upon relevant British or European standards. The police backed Secured by Design (SBD) scheme is another good check on overall security, as 'approved' products must be certified as meeting all relevant BS/EN or other relevant UK standards.

Insurer’s Minimum Security Standards
When insurance is sought against theft, its provision may be conditional upon premises having a certain level of physical security, often termed ‘Minimum Security Standard’ (MSS), or maybe Minimum Security Requirement or Condition.

MSS tend to concentrate on the fitting and use of common locks on typical doors and windows and may vary according to the insurer, type of property, e.g. domestic or commercial, or the type of insurance contract. The RISCAuthority, the UK insurer’s technical body has published a useful guide on the subject of MSS at homes - see Sources of Further Information.

Key Action Steps

  • Review current locks used at your premises, including any outbuildings, and ensure that they are correctly fitted to, or within, a door/window of suitable material/thickness.
  • Check whether any insurer MSS applies; and if so that you do comply, or that you have their agreement for any alternative arrangements.
  • Seek independent crime prevention advice, e.g. from the police or your insurer.
  • Source locks and security devices from competent locksmiths, e.g. a member of the Master Locksmiths Association (MLA).
  • Review security in the event of any loss. If you do not do so are at high risk of a repeat incident.

Sources of Further Information

Other ‘Hardfacts' in the Property Protection - Security series, which are available in our ‘Knowledge Store' at

Your local police Crime Prevention Unit

Your insurance broker or insurance company

British Standards Institution (BSI). Tel 020 8996 9000 or visit

Master Locksmiths Association (MLA)/Sold Secure. Tel 01327 262255/264687 or visit /

The Door and Hardware Federation (DHF). Tel 08127 52337 or

The RISC Authority (the UK insurers' technical advice body) see

In particular see:-



Loss Prevention Certification Board (LPCB), Tel 01923 664100 or visit

Secured by Design (SBD) Tel 020 7084 8962 or visit

Next Steps:

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Please Note
This document contains general information and guidance and is not and should not be relied on as specific advice. The document may not cover every risk, exposure or hazard that may arise and Aviva recommend that you obtain specific advice relevant to the circumstances. AVIVA accepts no responsibility or liability towards any person who may rely upon this document.

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