A night latch is a surface-mounted door lock that can be installed on the interior of any door. Night latches are easier to install than standard deadbolts and provide a similar amount of security.

Step 1: Choose between a standard night latch or a surface-mounted single cylinder deadbolt. Both install in the same manner, but the night latch can be set to lock automatically when the door is shut.

Step 2: If the night latch came with a mounting template, tape the template on the inside of the door to facilitate installation.

Step 3: Use a paddle bit or a hole saw to drill a 1-1/4 inch hole. The center of the hole should be 2-3/8 inch from the edge of the door.

Step 4: From outside, slide the cylinder ring onto the lock cylinder and insert the cylinder through the hole in the door.

Step 5: On the inside, position the back plate over the hole and connect the back plate to the cylinder using the two mounting screws that came with the night latch. Depending on the thickness of the door, it may be necessary to shorten the length of the screws. This is best accomplished by using a hack saw to cut the screws. If possible, thread a nut onto the screw before cutting it. Once the screw is cut, thread the nut off the screw to help realign the threads on the screw.

Step 6: Once the cylinder is secured in place, use a pair of tin snips or side cutters to shorten the connecting bar so it protrudes 3/8 inch from the door surface.

Step 7: Insert the connecting bar into the slotted portion of the night latch lock and position the lock into place.

Step 8: Use a pencil to mark the screw positions on the door. Remove the lock and drill 1/8-inch pilot holes for each screw.

Step 9: Reposition the lock on the door and secure it into place using the mounting screws and pilot holes.

Step 10: Close the door and place the strike plate in position. Use a pencil to mark the screw holes and drill 1/8-inch pilot holes before screwing the strike plate onto the door jamb. In some cases it may be necessary to chisel away a portion of the door jamb to allow the strike plate and lock to seat together properly.