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Mortice Lock

When choosing a mortice lock there are a few factors to consider.

  1. Dead or Sash Lock
  2. Size
  3. Security Level
  4. Colour

Deadlock or Sashlock

Mortice locks are available in 2 versions, deadlock with just locking bolt operated by key and sashlock with locking bolt and latch bolt operated by handles.

Size of mortice lock

Mortice locks were first introduced into the UK market when everything was still measured in inches.  Two standard sizes of mortice locks were created 2 1/2" and 3", these sizes have today been transferred into 64mm and 76mm, these sizes represent case depth, i.e. how far lock case goes into door, measurement A on illustrations below.  These standard lock sizes were created to accommodate various door and door frame styles, essentially the 76mm version moves the key hole and handles slightly further away from door edge and door frames, allowing adequate space to operate locks and fit appropriate door furniture.

Mortice Deadlock


A-Case Depth, B-Backset,

C-Case height, D-Forend Length

E-Forend Width

Mortice Sashlock


A-Case Depth, B-Backset

C-Case height, D-Centres

E-Forend Length, F-Forend Width

The above diagrams shows the important measurements to take when specifying a mortice lock.  After Case depth, backset (measurement B) is the next crucial dimension, as this determines the position of the keyhole and spindle hole for door handles.

Security Level of Mortice Locks

Mortice lock security levels are measured by levers, levers are the internal locking parts of a mortice lock, the more levers the more secure the lock.


When fitted not much of a mortice lock is visible, only the plate covering forend and keep can be seen, these plates are supplied with a colour of your choice, but normally Brass or Satin.  Often deadlocks are supplied with key hole plates or escutcheons these are supplied to match forend and keep.

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