Mortice Deadlock Measurement
Quick and simple guide to measuring a Mortice Deadlock.
A - Lock Depth
B - Backset
C - Case Height
D - Forend Lenght
E - 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 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 deadlock 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 on all deadlock pages of this site.