If you want extra security on an exterior door, consider installing a night latch. A night latch installs on the inner face of the door, and is easier to mount than a deadbolt lock. The night latch locks come in single models that lock from the inside only or double action, which lock from inside and outside. Here are some tips to install a night latch.

Prepare to Work

For this project, you need:

• safety glasses
• work gloves
• pencil
• masking tape
• tape measure
• framing nail and hammer or awl
• cordless/power drill with screw tip attachment
• coping saw or hammer and chisel, pliers
• hacksaw
• night latch kit

Choose a comfortable height to install the lock, and mark it with pencil. The typical height for installing a night latch is 48 inches from the floor, but you don't have to follow any set rules. Tape the template from the kit to the door, lining up the crease with the crease in the door edge.

Drill the Hole

Check the instructions to determine the diameter of the hole to drill for the lock, which is commonly 1¼ inches. Wearing safety glasses and work gloves, drill the hole from both sides of the door to keep wood from splitting. Don't angle the drill. Drilling key holes at an angle makes the keys and knobs too tight. 

Cut starter dimples for screws with the awl, or hammer and framing nail, using the screw graphics in the template as a guide, then detach the template. You may need to shorten the length of screws with a hacksaw based on thickness of the door.

Mount the Lock and Strike Plate

Push the shank of the latch back into the body by twisting the knob. Insert the latch in the hole, and align it with the screw dimples on the door. Drive the screws in with the drill bit, making them secure, but not too tight.

Place the strike plate on the interior face of the door jamb, or on the outer edge of the jamb based on design of the lock. Twist the knob to extend the shank, close the door, and mark pilot holes for the screws where the top and bottom of the shank come into contact with the jamb.

Lay the strike plate aside, open the door, and drill 1/8 inch holes in the jamb. Alternatively, cut the screw holes with a coping saw or hammer and chisel. Fasten the strike plate in the pilot holes with the screws.

Test the night latch to ensure it works correctly. If it doesn't work correctly, or you need a keyed lock installed, contact a locksmith.