How to Install a Mortice Lock

Begin by determining the height of the lock on your door. Hold the lock against the door with the lock face flush with the door edge. Mark the top and bottom of the keyhole. Also mark the top and bottom edges of the lock face on the door edge. Use a bradawl to get the hole for the keyhole started.

Place the lock faceplate in line with the markings already made on the door edge to determine where the timber needs to be removed from the door in order to allow the body of the mortice lock to slide into the door.

The keyhole is the first timber to be removed from the door. To avoid damage to the front surface of the door, clamp a piece of wood to the back of the door. Drill right through the door at the mark made previously. When the drill bit emerges from the back surface of the door, it will not tear timber fibres and spoil the surface.

Enlarge the hole into a slot by using the drill and hammer and chisel as necessary.

Choose a drill bit a little larger than the width of the lock housing. Set the depth gauge on your drill just a little deeper than the depth of the lock. Keep in mind that the lock faceplate will ultimately be recessed into the door as well as the body of the lock.

Use the drill to begin to form the mortice recess in the edge of the door to the required height and depth. Ensure the drill runs completely parallel to the sides of the door or the lock will not sit straight in the hole. Drill at 45 degrees upwards from the bottom hole and 45 degrees downwards from the top hole to reduce the amount of timber you need to remove with the chisel.

Using a hammer and chisel, enlarge the drilled holes as required. Do this step slowly, removing small pieces of timber at a time.

When the mortice recess is the correct size insert the lock. Push the lock in until the faceplate comes up against the edge of the door. Draw around this with a pencil to show the timber that needs to be removed in order for the faceplate to sit flush with the edge of the door. Using the chisel and hammer, chisel along the lines to a depth of 3mm, and then remove the timber carefully to create the recess for the faceplate.

Insert the lock and faceplate and screw in firmly. Check the position of the keyholes to ensure smooth operation of the key action.

Fit the keyhole covers on both sides of the door.

With the door open, turn the key in the lock to extend the bolt fully. Close the door so that the bolt touches the door frame. Mark the position of the top and bottom of the bolt on the door frame. Measure carefully to find the correct position of the striking plate or bolt receiver. Drill and chisel out a recess to allow the striking plate to fit flush in position.

Check the lock action with the door closed to ensure the position of the receiver/striking plate is correct, then screw it into position.