How to Replace a Mortise Latch with a Mortise Lock

What You'll Need
Flat-edge Chisel
Bevel-Edge Hammer
Cutting Tools
Mortise Lock
Clean Cloth

The mortise lock is preferred by homeowners today due to its durability and ability to lock doors, unlike the mortise latch. Mortise locks and latches are mechanisms that require a rectangular hole in the door edge for installation. Changing your mortise latch with a mortise lock is easy if you have right tools available.

Step 1 – Remove the Mortise Latch

Remove the mortise latch by taking off both knobs and the shaft. This is done by loosening the setscrew on one of the knobs, then pulling it off. Please note that some knobs screw onto the shaft. Take out the two latch retaining screws and pry the mortise latch out.

Step 2 – Mark the Mortise Center Line

Make a mark on the mortise center line by using a pencil and the lock as a template. Ensure that the mortise plate or lock is centered on the cross bore hole. This is to guide you where to chisel out the wood of the door so that the mortise plate fits perfectly level on the surface. It is advisable to use a sharp pencil so that your mark is right next to the edge of the plate. If the pencil is not sharpened, you'll end up with a hole that is too big and it won't look as good once the installation is done.

Step 3 – Square the Edges

Take out the waste and then using a chisel, square the mortise edges until the lock fits snugly. Use a sharpened chisel so that it will be easier to do the job and the end result will be much cleaner. First step is to use the chisel to score the perimeter of the area with the chisel. This will help you box the area that will be removed. If you don’t score the perimeter, you might end up removing material that is past the marked area. The result will not look clean and professionally completed.

Step 4 – Mark the Edges

Make a mark around the edges of the protective covering with a knife. Use a high speed cutter to shape the hole until the protective covering is even with the door. It’s important that the plate is level. If it’s not level, the door will shut incorrectly or may not even close at all. The finished look itself is better when there are no protruding plates on the surfaces.

Step 5 – Screw the Lock

Put the lock into its position by screwing it in place with the screwdriver. Work out the lock to see if it works. Shut the protective covering and keyhole enclosure on all sides of the holes.

Step 6 – Close the Door

Close the door and work the bolt to determine the position of the strike plate on the frame of the door. Most locks come with a marking device. Use the marking device to help you determine the position of the plate. Carbon paper may also be used as a marker.

Step 7 – Hack the Mortise

Make a mark and hack accordingly the mortise and cavity for the strike plate.

Step 8 – Mount the Strike Plate

Mount the strike plate into the cavity and screw it in place. Clean the mortise lock and test if it’s working properly.