A mortice lock is a common door fitting, where a spring-loaded catch or bolt, with a flat face and curved edge, engages in a recess in the door frame. As the door is pushed shut the curved face hits the striking plate on the door frame and pushes the bolt back into the latch body. When the door is fully closed the bolt springs out into the recess in the stroking plate with its flat face providing a positive latching action. Here are some instructions on how to fit a mortice latch to a door.
1. The latch is normally placed in line with the central panel width of a door.
2. Use the latch body to mark the mortice position on the door edge. In line with the centre rail or lock block.
3. Using a marking gauge, set it to just wider than the thickness of the latch body and mark the outline of the mortice centred on the door edge.
4. Using a power drill and flat wood bit make a series of holes between the guidelines, a little deeper than the length of the latch body.
6. Draw around the latch faceplate on the edge of the door then cut around the lines with a chisel and make a series of parallel cuts across the grain.
7. Carefully chisel out the waste wood between the marked guidelines.
8. Hold the latch body against the face of the door in line with the mortice and with its faceplate flush with the door edge. Mark the spindle position.
9. Clamp a spare piece of wood to the other side of the door. Drill a hole big enough to accept the spindle through the door into the scrap wood.
10. Slide the latch into place in its mortice and make pilot holes through the faceplate with an awl then drive in the faceplate fixing screws.
11. Insert the spindle and fit a handle onto each end of it. Check that the spindle rotates freely, then screw both handles to the door.
12. Close the door in order to mark where the latch bolt meets the frame, then chisel out the recesses for the bolt and striking plate.
13. Screw on the plate.