How to measure a Mortice Lock
Used in traditional timber doors a mortice lock is embedded in a door. Available as either a deadlock or sashlock. Please note this guide covers ERA mortice locks only, it’s always advisable to refer to the individual manufacturer's instructions for the specific product details.
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How to measure a mortice lock
When fitting or replacing a mortice lock there are a few measurements required to ensure that you purchase the correct lock for the application. A drawing of the individual lock (found in the fitting instructions or technical data sheet) is useful for routing information if you are fitting the lock into a new door.
The five key dimensions are shown in the diagram below (sashlock shown):
Dimension A: Backset
Backset is measured from the centre of the keyhole to the edge of the lock. Most backsets are commonly measured at either 44mm (for a 64mm (2½”) lock) and 56mm (for a 76mm (3”) lock). Typically a lock adjacent to a glass panel will be 2½” (44mm) and otherwise 3” (56mm), but you should always measure to be sure.
Dimension B: Centre (Pz)
Measured from the centre of the keyhole/ cylinder to the centre of the follower hole (the square hole the handle spindle passes through). This dimension isn’t required for a deadlock as there is no handle.
Dimension C: Case depth
The depth of the lock when routed into the door, measured from edge to edge. Typically in the UK case depths are generally either 64mm (2½”) and 76mm (3”). However, please check before installing, especially if you are replacing an existing lock.
Dimension D: Case height
The height of the lock case, measured from top to bottom.
Dimension E: Forend (faceplate) length
The overall length of the forend/faceplate (the part that is visible once the lock is fitted). The end of the faceplate may be squared or round.
Dimension F: Forend (faceplate) width
The width of the forend/faceplate (the part that is visible once the lock is fitted). The end of the faceplate may be squared or round.
Terminology
Sashlock
A lock mechanism incorporating both a latch and deadbolt feature. Sashlocks can be key operated with a lever mechanism or cylinder operated and can incorporate thumbturns for keyless egress applications. Typically used with a lever handle set.
Deadlock
A lock mechanism incorporating a deadbolt only. Deadlocks can be operated with a lever mechanism or cylinder operated and can incorporate thumbturns for keyless egress applications.
Latch
A self-engaging element of the lock that secures the door when engaged with the keep, and can be released by hand. Latches can be deadlocked so that when the lock mechanism is engaged, the latch cannot be withdrawn.
Deadbolt
A bolt that is operated in both directions by a key, handle or thumbturn.
Differ (effective differ)
The difference between locks of similar design, achieved by the levers, allows each lock to be operated by its own key.
Forend (faceplate)
The element of the lock case through which the lock is fixed to the door, and through which the latch and or deadbolt pass. Faceplates may have a square or round end.
Spindle
The square section drive bar, usually 8mm in width that is positioned through the drive of the lock and locates into the handle set levers, or knobs. Operating the lever rotates the spindle, which in turn operates the drive (follower) of the lock. The required length of the spindle is dependent upon the thickness of the intended door and the depth of the receiving element of the handle lever.
Centres
The vertical dimension between the lock spindle and the centre of the keyway of the gearbox. Centres can vary between lock systems, though the ERA range has a standard of 57mm. Understanding the lock centre dimension is critical for the specification of the correct handle.
Rebate
A rectangular recess along the edge of a frame to receive the corresponding door leaf. Rebates are also machined into the meeting rails of double doors to provide closing faces for the corresponding leaves. Rebate conversion kits are required for door locks and keep, fitted into rebated edges of timber doors.
Backsets
A backset is the distance between the lock keyhole and the outer edge of the lock.
Keeps/ Striker
The element of the lock system that is fitted to the fixed portion of the door frame, into which the moving part of the lock (e.g. bolt) engages when in the locked position.
Need further help?
If you have any questions, please contact the ERA Expert team who would be happy to assist. Or for further details ERA has a broad range of mortice lock solutions to suit the majority of applications. For more information visit eraeverywhere.com
