Having to change a Mortice Lock can be inconvenient, so knowing how to select the correct sized replacement lock can help speed up the process.


There are two different kinds of Mortice Locks: A Sashlock and a Deadlock.


Knowing which type of Mortice Lock you are replacing is very important to taking the measurements needed.


A Mortice Deadlock is more typically used on front doors. It has a bolt operated by a key.

For a Mortice Deadlock you should only require the measurements of the Backset or the Case.


This is the measurement from the front plate to the back of the lock case or the back of the slot the lock fits into in the door.



Mortice Deadlock Case Width 


If you have the old lock this measurement can be easily taken with a ruler or tape measure. If the lock is still in the door it is possible to measure from the front plate of the lock to the centre of the keyhole. If the measurement is 45mm, you need a 64mm (2.5") mortice lock. If the measurement is 57mm, you need a 76mm (3") mortice lock. These measurements are approximate.


A Mortice Sashlock is more likely to be used on back doors and internal doors. It has a bolt operated by a key but it also has a latch operated by a handle. These offer security through the bolt and convenience through the latch.

For a Mortice Sashlock you should know the measurement of the case width and also what is known as the ‘Centres’ measurement. This is the distance from the centre of the keyhole to the centre of the Door Handle Spindle Hole. It is important to know this measurement when buying your replacement lock so there will be no need to replace door handle sets or for drilling more holes.


Mortice Sashlock Centres Measurement