Deadbolt locks provide extra security for entry doors. There are two types -- single-cylinder and double-cylinder. Single-cylinder types feature a finger latch that can be opened from the inside. Double-cylinder deadbolts must be opened with a key from either side of the door.

Both types are available in a variety of styles and finishes to match existing hardware.

Measure to find the lock location. Tape the cardboard template, supplied with the lockset, onto the door. Use a nail or awl to mark the centerpoints of the cylinder and the latch bolt on the door.

Bore a cylinder hole with a hole saw and drill. To avoid splintering the door, drill through one side until the hole-saw pilot (mandrel) just starts to come out the other side. Remove the hole saw and then complete the hole from the opposite side of the door.

Use a spade bit and drill to bore the latch bolt hole from the edge of the door into the cylinder hole. Make sure to keep the drill perpendicular to the door edge while drilling.

Insert the latch bolt into the edge hole. Insert the lock tailpiece and connecting screws through the latch bolt mechanism, and screw the cylinders together. Mark the edge of the latch with chalk and close the door. The chalk will mark the door jamb, indicating where to properly place the strike plate.

Cut the outline of the mortise by holding a chisel with the bevel-side in and tap the butt end lightly with a mallet or hammer until the cut is at the proper depth.

Make a series of parallel depth cuts 1/4 inch apart across the mortise with the chisel held at a 45-degree angle. Drive the chisel with light mallet blows to the butt end of the chisel.

Pry out the waste chips by holding the chisel at a low angle with the bevel-side toward the work surface. Drive the chisel by light hand pressure.

Bore the latch bolt hole in the center of the mortise with a spade bit. Install the strike plate using the retaining screws provided with the lockset.