How to Measure a Mortice Sashlock
When replacing a lock or specifying new locks, the size is vitally important, this guide shows the methods required to measure a mortice sashlock.
A - Case Depth, measurement taken from forend to end of the lock case
B - Backset , distance from forend to centre of keyhole and centre of latch spindle
C - Case Height, the height of the lock case
D - Centres - Distance between Centre of keyhole and handles
E - Forend Length, this is the section of the lock that is visible when fitted into a door.
F - Forend Width
Lock measurement can seem like a black art! But follow this simple guide and you cannot go wrong!
Most important measurements are the Backset and Case Depth, these determine the distance from the edge of the door the key hole and handles will be, important for doors with large or ornate frames with limited clearance. Standard Case Depth sizes are 64mm (2.5") and 76mm (3") and standard Lock backset sizes are 44mm and 57mm, a 50mm case size is also available for doors with a narrow stile or aluminium doors.
Other lock measurements although important are not so critical, these include Case Height, Forend Length and Width.
To replace a sash lock like for like, first remove lock from door, place on a flat surface with forend on left side, then measure A-E, these corresponding sizes can be found at the bottom of all mortice sashlock products on this site.