How to fit a door lock (mortice, tubular latch and cylinder)

Step by step

1. 1Choose the position

   A mortice lock normally sits with its centre level with the middle rail, around 990mm–1000mm from the floor. Never cut the mortice through a joint between stile and rail.

2. 2Mark the backset and centre line

   Hold the lock against the face of the door in its exact position and pencil round the case. Use a marking gauge from the door face to set the centre of the door edge so the mortice sits dead centre.

3. 3Drill the mortice

   Choose a bit the same width as the lock body and drill a line of overlapping holes along the centre line, slightly deeper than the lock case. A depth stop or tape on the bit keeps you from breaking through.

4. 4Chop it square

   Pare the mortice square with a chisel until the lock slides in with light hand pressure. Then mark round the faceplate, cut the recess and check it sits flush with the door edge.

5. 5Drill the spindle and keyway

   Mark the spindle and key positions from the lock itself onto both faces of the door, and drill from each side to meet in the middle so you don't blow out the far face.

6. 6Fit the keep and test

   Close the door, mark where the bolt meets the frame, cut the keep recess and fit the striking plate. Test the key and handle with the door open and closed before final tightening.