How To Fit A Mortise Lock

Step 2: Mark the lock position

Decide on a height for your lock. Hold the lock flat against the door edge at your chosen height, and draw around it with your pencil. Use your tape measure to find the centre point on the side of the door. Mark it with a pencil and draw a longer vertical line through the point.

Step 3: Select a drill bit

Select a flat drill bit that is roughly 2mm or 1/16th inch thicker than the lock body. This will ensure a comfortable fit. Hold the lock against the drill bit. Use the masking tape to mark the depth of the lock on the bit, and attach it to the drill.

Step 4: Drill

Before you start drilling, remember your drill safety. Put on your goggles. Make sure all loose items of clothing, jewellery and hair are tucked away. Clear the area of any potential hazards and find a steady standing position.

You may want to wedge the door open to help steady your drilling.

Start just beneath your top pencil mark and drill a series of overlapping holes down to your bottom pencil outline. Drill to the depth marked and take care to keep the bit horizontal and square to the door edge.

Step 5: Straighten up the edges

Before you pick up your chisel, remember your chisel safety. Make sure that you are wearing safety goggles and clear the area of potential hazards. Find a steady position and remember to watch your fingers when you do start chiseling.

Firstly clear out any wood chippings with the chisel. Then use your chisel to tidy up the edges of the mortise recess so that the mortise will fit. Keep the flat edge of the chisel facing outwards as you work and chisel to the depth of the recess. Scrape out any woodchips.

Step 6: Mark the face plate

Now slide the lock into the recess and place the face plate over it. Draw around it.

Step 7: Make a recess for the face plate

Begin by making a series of cuts on the edges of your pencil outline. Now chisel out the rest of the recess. Be careful, because if you chisel out too large a recess, it will be difficult to correct.

Keep testing the fit to see that the face plate lies flush with the door.

Step 8: Mark the key holes

Hold the lock against the face of the door so that the plate is flush with the door edge. Mark through the key hole with your pencil, and then do the same on the other side of the door.

Step 9: Drill the key holes

Select a drill bit that is a little larger than the key hole, and insert it into your drill.

Remember your drill safety.

Drill along one pencil line through to the lock recess. Repeat this on the other side of the door.

Step 10: Test the key hole

Insert the mortise into its recess and check that the key works smoothly.

Step 11: Attach the face plate

You may want to drill small pilot holes for these screws, but in most cases you can just drill them straight in.

Step 12: Fit keyhole cover

Hold the key hole over the key hole and drill it into place. Repeat on the other side of the door.

Step 13: Mark the bolt position on the frame

Turn the key to extend the bolt. Push the door to, and draw around the bolt on the frame.

Step 14: Mark the strike plate position

Measure the distance between the inside edge of the door and the strike plate. Mark this measurement on the door frame. Align the strike plate with the pencil line you have just made. The bolt recess must be positioned according to the marks on the edge of the frame. Draw in and around the strike plate.

Step 15: Cut bolt and strike plate recesses

Remember your chisel safety. Following your marks, chisel out a hole for the bolt. First cut around your pencil outline, then chisel out the recess. Check the fit of the bolt in the recess.

Then chisel out a shallow recess for the strike plate so that it lies flush with the door frame. Be careful not to chisel too deep a recess as this will be hard to undo. Keep testing the pate until it fits snugly.

Step 16: Attach the strike plate

Remember your drill safety. Drill the strike plate into the frame.

Step 17: Test

Now test your handy work. Check that the door closes easily and that the key turns smoothly.