Anti Thrust Bolt - A spring bolt, for a night latch particularly, which cannot be pushedback when it has shot out  and fastened a door, although it can be withdrawn by knob or key.  This security device is usually achieved by a dog inside the latch case which falls behind the bolt and keeps it shot out when an auxiliary slide is pushed in. 

Anti-thrust plate - An overlapping metal plate fitted to outward opening doors so as to prevent access to lock bolts. 

Automatic Deadlatch - A deadlatch, the main bolt of which is automatically locked (or deadlocked) when the door is closed.  


BackcheckThe feature of a door closer unit that prevents shock and possible damage when the door is forcibly opened.

Backplate - The plate, fixed on a door, to which the moving parts of a lock or latch are attached.  

Backset -  The horizontal distance from the outside face of the outer forend to the centre of the keyhole or follower hole (or both). Designated as the “keyhole backset” or “follower backset”.

Barrel - A cylindrical portion of the cylinder that rotates when the correct key is used. 

Barrel Bolt  - The common kind of door bolt having a round shoot running in a long continuous guide or strap attached by the backplate, the shoot being provided with a knob or the equivalent for operation by hand.

Bathroom Lock - A mortice lock which is used with thumbturn handles to allow the occupant of the bathroom to lock the door from the inside. 

Birmingham Bar - A steel bar fitted to the inside face of a door frame on the hinge side.  

Blank (key) or key blank - A partly made key, which has been shaped to enter the keyhole of a certain type of lock or latch, but of which the blade has not been finally notched to operate any individual lock.  

Bolt  - The part of a lock or latch which provides the fastening or engagement by protruding from the case or forend to engage in the staple, striking plate, link, shackle or other member. 

Bow (of key) - That part of the key which is held in the fingers when operating the lock or latch.

Box Strike - A strike in which the latch bolt recess is enclosed or boxed, thus covering the opening in the jamb. 

BS - British Standard Specification Authorised and issued by the British Standards Institute, the accepted UK authority for all standards of performance, tests and manufacture.

BS EN 1303 This standard classifies cylinders using a 7 digit coding system.  Each digit refers to a particular feature of the product measured against the standard's performance requirements.  The standard includes tests on durability, fire and corrosion resistance. 

BS 3621 - The British Standard specification for Thief Resistant Locks for hinged doors. Locks submitted for certification must satisfy the requirements of the ten stringent clauses of the specification. This British Standard applies to Mortice Locks and Nightlatches.  All locks that carry the BS3621 kitemark meet the standards set by insurance companies and the police.

BS7950 The British Standard that relates to the enhanced security of windows. 

Burglar Bars  - Steel bars, usually round or square in profile, cut to length and fixed internally to window frames.

Butt Hinge (for Doors) Hinges are designed for timber doors, purchased pre assembled and fitted on site to enable doors to be hung.


Cabinet lock - A generic term to include all locks of any type for use on pieces of furniture, such as cupboards, drawers, chests, boxes and the like. 

Cam - Usually a tongue fixed to the end of the plug of a cylinder lock or latch. This activate

Cam lock - A complete locking assembly in the form of a cylinder whose cam is the actual locking bolt. 

Cap (of the lock) - The removable cover to a lock mechanism. 

Casement Door  - A hinged door or pair of doors almost wholly glazed; often called a French Window. 

Casement Window - A window in which one or more lights are hinged to open.

CE Marking - CE Marking on a product is a manufacturer's declaration that the product complies with the essential requirements of the relevant European health, safety and environmental protection legislations, in practice by many of the so-called Product Directives.

Centres - The vertical measurement in an upright or sash lock between the centre of the keyhole and the centre of the follower hole.  

Circlip - A ring with open ends which can be sprung into place on a plug or other part to permit rotation but to prevent endways movement.

Closed shackle padlock - A padlock, the body of which is built up so that the minimum amount of shackle is visible when locked. It offers improved security against forcing or use of bolt-croppers.  

Combination Lock - An abbreviation of name for a keyless combination lock.

Cut cabinet lock - A cupboard or drawer lock, the flange of which is recessed into the edge of the drawer or door. 

Cylinder - Usually the cylinder with inner co-axial plug which houses the pins, top pins(drivers), or disc tumblers and springs in the cylinder body.  

Cylinder housing - With all component parts removed, this forms the main body or housing of a cylinder. 

Cylinder key - A key, having a bow and long blade in which “V” cuts are made along the 
upper edge to operate the pins and drivers in a pin tumbler mechanism. 

Cylinder lock or latch - Any lock or latch, the mechanism of which is contained in a cylinder. 

Cylinder rose (or ring) - A shaped metal disc which surrounds the outer face of the cylinder of a cylinder mechanism assembly. It usually stands slightly proud of the outside face of door. 


Deadbolt  - The square-ended bolt of a lock which is moved in both the locking and unlocking directions by the key (but occasionally by thumb turn inside only) to provide fastening.  N.B. For obvious reasons, it is inadvisable to incorporate the thumb turn with the deadbolt of any deadlock or lock which is supposed to offer good security, if used on glass or wood panelled doors. On a mulit-point lock, the deadbolt is located at the centre of the lock to add increased security. Normally of rectangular shape but can also be in the shape of a hook.

Deadlatch - A nightlatch or latch, the springbolt of which can be locked (or deadlocked) by key or other means. 

Deadlock  - A lock having only a square-ended deadbolt operable from one or both sides by key, and occasionally from outside only by key, inside by thumb turn. Sometimes operable only from outside and with no inside keyhole, which is designated a single-entry deadlock. Some nightlatches have a deadlocked function that adds extra security to the locking mechanism after the key has been rotated for a second time.

Delayed Action - A feature of a door closer which holds the door in the open position for a number of seconds before the closing action commences. This feature is ideal for use by the handicapped, the aged and people with prams, trolleys, etc. The SAA Fire Door code approves the use of delayed action closers on fire doors. 

Detainer 1. A generic term, not widely used, for any part such as a lever or tumbler which keeps a lock bolt in position 2. The name of the sliding security members in Butter’s System locks. 

Differs  - An abbreviation of “different combinations” or changes. 

Disc tumblers - The small shaped discs (usually of metal) in the disc tumbler mechanism which are the means of providing different combinations.  

Disc tumbler lock - A cylinder lock having disc instead of pin tumblers.

Door Chain - Also called Door Limiter. A fitment that restricts the door to being partially opened in order to identify callers prior to opening the door for access. Can be either an integral part of the lock mechanism or surface mounted on the inner face of the door.

Door Limiter -  See Door Chain

Door Closer - A device for closing a door or gate automatically after opening. There are numerous types available. 

Door viewer - Optical device fitted through a door to enable observation without opening the door. 

Double Bitted Key - One with a bit on each side of the shank. 

Double-handed lock - (1) A lock designed for use either as a right or left hand installation without alteration, generally by turning upside down. The keyhole has a circular formation at each end of the slot to accept the shank of the key. (2) A cupboard lock, the bolt of which can be shot either way to protrude from either side of the case.

Double locking - Where a lever lock shoots its bolt by more than one turn of the key, thus doubling the distance of its shoot. 


Escutcheon - The cover for the keyhole of a mortice or similar lock.

Electrical Strike - An electrical device that permits releasing of the lock in the door from a remote control.

Espagnolette - Another term for multi-point locks usually used on windows.

Espag. - See Espagnolette

Euro Profile Cylinder - A cylinder barrel with a specific shape that can be fitted and used in many types of locks including mortice locks and multi-point locks.


Face plate - The outer of a double forend. A strip of metal fixed to the inner forend, thus forming a double forend.

Final exit door - The exit door through which entry must later be obtained, and so cannot be bolted. It is usually the front entrance door or final means of exiting.

Finish - Final cover treatment of the product for appearance and protection, in both plated finishes or powder coat colour.

Flag Hinge (for doors) - Door Hinge system used on PVCu Doors which allows for easy installation and adjustment.

Flush Bolt - A door bolt which can be recessed flush into the edge or face of a door

Follower Also called RowerA square hole created in the backset of a mortice lock to allow the spindle to feed through to operate the handle. 

Forend - That part of the lock or latch through which the bolt(s) protrude, and by which 
the lock or latch is fixed to the door.

Furniture - The additional items needed, which are screwed to one or both sides of the door to enable a lock or latch to be manually operated. Known as door furniture, lock or latch furniture, locksets or latchsets (when complete with lock or latch) and can be either knob, lever handle, pull handle or push button.



Handed Products - A product designed or assembled for use only on right hand doors or only left hand doors, but not both.

Handing - The direction of door travel (swinging or sliding) and the locking/secure side of a door, eg. Right hand (opening out), left hand (opening out).

Hasp and staple - A fastening in two pieces for a door or box to be secured by a padlock. The hinged part is called the hasp which is fitted to the door or lid of a box and shuts over the staple, which is on the door frame (or other leaf of a pair of doors) or the body of the box. For real security it is essential to use a hasp and staple with concealed fixing, i.e. the heads of the fixing screws are completely covered when the padlock is locked in position, as otherwise the fitment can easily be removed by withdrawing the screws affording nil security.

Hinge Bolts - Fixed steel protrusions fitted into the rear edge or hinge side of doors, closing into holes cut into the door frame, to protect from forced attack on the hinge side of the door.

Hold Back A catch or other device on a lock which can hold the latch bolt in the retracted position.

Hold Open - The feature of a door closer unit which enables a door to be held in the opened position until released.

Hook bolt A pivoted springbolt, the head of which is shaped in the form of a hook. Such locks or latches are usually fixed on sliding doors and multi-point locks. Designed to assist door compression and a high level of security against forced attack.


Indicator Bolt A slide-action bolt installed in areas where privacy is desired (such as toilets and bathrooms) which provides visual indication that the room is occupied or vacant.


Jamb - The vertical member of a door or window frame. In some areas the top rail of a door frame is referred to as the top jamb.


Keep - A metal plate or box which is pierced or recessed to receive the bolt or latch when projected.

Key - A small removable device for operating the mechanism of its own lock, locking latch or nightlatch. 

Key blank - A partly-made key, which has been shaped to enter the keyhole of a certain type of lock or latch, but of which the blade has not been finally shaped (i.e. notched or bitted) to operate the mechanism of the lock.

Keyed Alike - Indicates identical key for 2 or more locks.

Keyed to Differ -  A different key is needed to activate each lock.

Keyhole - The hole into which the key enters to operate the lock or latch. It is often referred to as the keyway, particularly in a cylinder mechanism.

Kitemark - A BSI Kitemark is a trusted mark/symbol of product quality recognized by consumers and specifiers. Kitemarked products have passed a rigorous certification process and can be repeatedly manufactured and supplied to the same standard and purpose for which they were designed.

In addition to this, the products and quality management systems of Kitemark licensees are audited periodically to maintain product quality under ISO 9001: 2000 



Latch - The type of product with one bolt only, the bevelled springbolt or roller bolt, to latch or fasten the door, but not capable of being locked. Certain types, e.g. locking latches, nightlatches, or deadlatches, can, however, be locked by key or other means.

Latchbolt  - Most mortice sashlocks have an easily reversible latchbolt for securing the door so that it can still be operated by handle from either side. 

Lever - A flat shaped movable detainer in a lock, usually for the purpose of providing security and differs. The lever(s) in a lock have to be actually moved by the key to operate the lock. The belly of the lever is cut away to various depths to provide different combinations.  

Lever mechanism - A lock mechanism having, as its principle feature, one or more levers.

Lever and warded mechanism - The lever mechanism with the addition of wards, usually for providing a greater number of differs. The addition of wards does not, however, increase the security of a lock.  See “Wards”. 

Lever handle - A piece of lock or latch furniture, usually on a rose or plate, for use as an alternative to a knob for operating the springbolt of a lock or latch. All British lever handles are spring-loaded to ensure the return to horizontal after use, but Continental lever handles are not usually spring-loaded and thus when used with British locks or latches, sometimes tend to sag below the horizontal after a comparatively short period of use, unless additional springing is included in the lock action. 

Lock - A device operated usually, but not always, by a key, having one or more bolts or other members to fasten and secure a door, lid, drawer or other member. 

Lockable bolt - A bolt that can be shot and locked in position by the use of a removable key.

Locking latch - A latch with a bevelled springbolt or roller bolt which is capable of being locked or secured, usually by key.

Locking Point - The point where the multi-point lock enters the outer frame of the door, using either a hook or a rectangular shaped bar. 

Lockset A lock complete with necessary furniture including a spindle, ready for fixing to the door.

Lockset furniture or lock furniture A lockset, minus the lock. 

London bar  - A steel bar fitted to the inside face of a door frame, shaped to accommodate the staple or striker of a rim latch lock.

Long shackle (LS) - A padlock shackle with a greater amount of clearance than the normal standard shackle. 


Master Key - A key which will open every lock in a master keyed suite.

Master Keyed (locks or latches) - A lock or latch capable of being operated also by a master key as well as its own change or servant key. 

Mortice - A hole cut into the thickness of one edge of a door to receive a mortice lock or 

Mortice Key - A key to operate a lever lock, consisting of a bow, shank and bit. 

Mortice lock (or latch) - A lock or latch which is morticed or let into the thickness of the door from the meeting edge and held in position by screws through the forend.

Multi-Point Lock - Describes a type of lock mechanism that has more than one locking point.  It usually has a minimum of three locking points (plus latch) spread strategically over the length of the door.  Multipoint locks are typically used on PVCu or composite doors. 

Mushrooms - Mushroom shaped locking pointss found on multipoint door locks.


Nightlatch - A rim or mortice latch with a bevelled springbolt or roller bolt which shoots when the door is closed, but can be withdrawn by key from outside and by knob or lever handle from inside. Usually provided with a stop knob, slide or snib to hold the bolt retracted and to deadlock the bolt when shot in the closed position, even against the action of the key.  Nightlatches are still sometimes referred to by their traditional name of 'rimlock' although a rimlock usually now refers to a basic security lock for use on internal doors, gates or outbuildings.

Non Handed - The ability to reverse the product or key component to suit left or right-hand installation.


One-sided lock (single-entry)  - A lock which has a keyhole on one side only, so that it can be operated by key from one side only, usually outside, but not from both. Nearly all cabinet locks and all padlocks are examples. Some high quality cylinder mortice locks are one-sided.

One-way action - An action where the follower will turn only one way.


Padlock - A comparatively small removable and portable locking device, usually but not always key operated on one side only. The locking member is a circular hinged sliding or swivelled shackle which passes through a hole in a staple, locking bar or similar member.

Panel grilles - Steel grilles made to size with various infills of expanded diamond mesh, square weldmesh or fancy infills, usually fitted internally. 

Parallel armed door closer - A type of door closer installation where the arm is mounted parallel to the door, for use where the door closer is installed on the inside of an opening out door.

Passage Set - A term commonly used to describe a latch set with handles on both sides of a door but no locking function.

Patio Lock - A lock designed with a pushbutton or turn button inside to lock the outside handle. When so locked, there is no entrance by key from outside.

Pin tumbler mechanism - The mechanism incorporated in the cylinder or body of a cylinder pin tumbler lock, latch or padlock, usually referred to as a cylinder lock, latch or padlock. Other than padlocks, the cylinder with its co-axial plug housing the pins and drivers under spring pressure passes through the thickness of the door, and the correct key lines up the pins and drivers to make a clear line of intersection between plug and cylinder, thus allowing the plug to rotate and the lock to be operated. The mechanism offers high security against key interchangeability and anti-pick mushroom drivers are usually included in every cylinder. For example, Yale 5 pin cylinders offer up to 24,000 differs as standard. It is also very suitable for master keying, as many different types of locks or latches can be included in the suite. Under master key, 12,200 differs are 
obtainable and under grand master key, 36 different sub suites with up to a total of 2,200 differs can be provided.

Plug - The part of the pin-tumbler cylinder mechanism or disc tumbler cylinder mechanism into which the key enters and which the key turns. It houses the pins of a pin tumbler cylinder mechanism or the discs and springs of a disc tumbler cylinder mechanism.

Privacy Set - A term for locks used on bathroom and bedroom doors having an inside button or turn knob to lock the outside handle and usually an emergency function which will unlock the set from the outside.



Rack Bolt - A bolt, usually a door bolt, which is toothed so that it may be operated by a pinion.

Rebate - The measurement of the stepped reduction or recess in the forend of a rebated lock.

Rebated Door - A door where the leading edge is stepped.

Rebated (lock or latch) - A mortice lock or latch with a forend specially shaped to correspond with the shaped meeting edge of the door for which it is intended. 

Receiver - A metal plate or box which is pierced or recessed to receive the bolt or latch when projected.

Release - A striker in various forms to replace the lock strike and is operated electronically. 

Reversible Lock - A lock with the components that can be readily adapted to enable the lock to suit door of either hand, opening in or out.

Rim Cylinder - This relates to a pack which usually comprises the cylinder with plug, rose, connecting bar, two connecting screws and two keys.  Normally used on Nightlatches.

Rim lock or latch - A lock or latch that is fitted by screwing on to the inside face of the door. 

Rose - (1) A cylinder rose or ring in cylinder locks or latches. It is a shaped metal disc which surrounds the outer face of the cylinder  (2) In door furniture, it is the small plate to which the lever handle or knob is affixed and which is screwed to the door surface.

Rower - See Follower


Safe Lock - A general term for the many varieties of key operated and other locks for safes.

Sash lock - An upright mortice lock, consisting of a latch bolt and a key operated bolt.

Sash ward - Used in rim and mortice locks, alone or in conjunction with levers for the purpose of obtaining or increasing the differs. Formed pieces of concentric metal are affixed around the inside of the keyhole. It also serves as a keyhole bush. The bitted key passes over these wards to operate the bolt. Little security is given when sash wards are used by themselves.    

Shackle - The hinged, sliding or swivelling loop shaped member of a padlock. The heel of the shackle remains always in the padlock body and the toe of the shackle comes out when unlocked. A double locking padlock gives the greatest security against forcing because there are two separate bolts locking outwards in opposite directions, one into a niche in the heel of the shackle, and the other into the toe of the shackle. This is sometimes called heel and toe locking.

Shear Line - The term is used to denote the line of the circumference of the plug in the bore of a pin tumbler cylinder. 

Shoot - (1) The outward movement of a lock bolt and the distance which it travels under the action of a spring or key. Shoot applies more particularly to spring bolts, throw being a better word for dead bolts. (2) The sliding part of a door bolt.

Shootbolt Shootbolts are used on multi-point locks to further secure the door into head and sill of the frame by an upwards movement of the sprung handle.

Shoot (of bolt) - The distance a springbolt moves under the action of its spring. 

Side Bar - This is in addition to the existing pin or disc mechanism, and is a bar usually along the length of the mechanism and does not allow rotation until the mechanism is correctly lifted and can be directly controlled by the key.

Side Wards - Notches cut into the sides of bitted keys so fashioned to enable the key to turn. 

Sliding Lever - A lever which slides between or on guides instead of swinging on a pivot.

Snib - A button or slider on a nightlatch that enables the latch to be “held back”, preventing the door from accidentally slamming shut. 

Spindle - That part of the door furniture usually of square section which passes through the follower hole and is fitted to the knob(s) or lever handle(s) to operate the springbolt. When the levers of your door handles are pressed, the spindle rotates and operates the latch inside the door, allowing the door to open.

Spring shackle padlock - A padlock, the shackle of which springs open when unlocked, and is locked by snapping to. 

Springbolt - Sometimes called the latchbolt. A bolt having the outer edge shaped by bevelling of the vertical face. It is a bolt which may be pushed back into the lock-case and will return to the extended position without mechanical assistance.  

Staple - (1) A box-like fitting on the jamb of an inward opening door, and into which the bolt or bolts of a rim latch or lock shoot when door is closed. (It is sometimes referred to in Scotland and the North of England as a Bosshead). Some staples are lipped to act as a guide for the springbolt. (2) Part of a hasp and staple for use with a padlock. The padlock shackle passes through the eye or hole in the staple.

Snib (Stop knob) - A device incorporated in some latches and locking latches to hold the bolt retracted or deadlock the bolt when door is closed. 

Striking plate - Sometimes referred to as a “striker”. It is a shaped flat metal plate fixed to the door frame or jamb with one or more bolt holes into which the bolt or bolts shoot. There is a shaped projecting lip on one side to guide the springbolt. It is used with all mortice locks or latches, and with rim locks or latches with reversed springbolt on an outward opening door.

Suite (of locks) - A group or collection of locks and/or locking latches and padlocks of different types and changes incorporated together under a master key or grand master key. 


Thumb turn - A small fitting, on the inside of a mortice lock, which is gripped between thumb and finger to operate the deadbolt. It should not be used on glass- or wood-panelled doors.

Time Lock - A clockwork or electric timing device which disallows operation of a lock or the opening of a door on safes or strongrooms.

Tubular Bolt/Latch - A bolt having a tubular case.






Wards - Fixed obstructions inside a lock case to preclude the use of wrong key, as the key is cut to pass over the wards and operate the lock. They are sometimes used in lever locks to give increased differs. Wards alone give very little security.  See “Skeleton Key”.  

Warded lock  - Any lock or padlock, the mechanism of which makes use only of wards. Not recommended, due to lack of security.







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