How to Install a Deadbolt Lock

The tool burglars favor most to break into houses is not a lockpick or a pry bar but a foot. With one or two well-placed kicks, they can tear out a door's strike plate and latchbolt and walk right in. A deadbolt lock makes an exterior door stronger because it bolts deeper into the door jamb than the bolt in a typical entry lockset. A deadbolt is a small investment to make your family feel safer and more secure.

Do It Yourself or Hire a Pro?
A locksmith will charge about $125 to install a good-quality deadbolt on an exterior wood door. You can buy and install one for about $35. If your exterior door is wood, installing a deadbolt is eminently doable. If you have a steel or fiberglass door, get a locksmith to do the job, because it takes a heavy-duty drill and bits to cut into these tougher materials.

Here's an overview. Installing a deadbolt involves drilling two holes in the door. One hole, in the edge of the door, receives the lock assembly; the other, in the face of the door, accommodates the lock cylinder. Then you drill another hole in the door jamb for the strike plate. The lock comes with paper templates that you tape to the door and the jamb so that the holes are correctly aligned. The final phase of the job involves assembling the lock mechanisms in the door and screwing the strike plate to the jamb, using extra-long screws.

Step by Step

1. Place the template and mark the door. Unfold and position the paper lock template on the door, then tape the template so it can't move. Transfer the centers of the lock cylinder hole and latchbolt hole by poking an awl through the marks on the template.

2. Drill the holes. Use a hole saw to start a hole for the cylinder in the door's side edge, stopping when the pilot bit breaks through the other side. (Drilling all the way through may cause the door to splinter.) Remove the drill and finish drilling from the opposite side of the door. Most locks require either a 2 1/8-inch or 1 5/8-inch hole. Use a spade bit (7/8-inch or 1-inch) to drill the hole for the latchbolt in the door's edge.

3. Install the latchbolt. Push the latchbolt into the door edge and mark the latchbolt plate's outline on the door's edge with a sharp pencil or a utility knife. Remove the bolt plate and carefully chisel a mortise so that the latchbolt plate is flush to the door end when you are finished.

4. Install the lock. Place the latchbolt in the door and screw its plate to the edge of the door. Then install the cylinder on the outside face of the door. The cylinder shaft must be slipped through the latchbolt assembly and mated with its complementary section, which is installed on the inside face of the door. Insert the long threaded machine-bolts and screw the two halves of the cylinder together. Tighten well.

5. Install the strike plate. Creating room for the deadbolt to slip into and mortising a hole for the strike plate is a two-step process. First, use the paper template to position the deeper of the holes for the deadbolt on the door jamb. Because the hole will eventually be rectangular, use a spade bit to bore overlapping holes in the jamb, then square off this cavity with a wood chisel.

The mortise for the strike plate, which is approximately centered over the deadbolt cavity, is wider and longer, but only as deep as the strike plate itself. Use a chisel only to cut the strike plate mortise, being careful not to split the jamb when the chisel blade is parallel to the wood grain. Then screw down the strike plate, using screws that are long enough to penetrate into the stud behind the jamb. Typically, such screws are 3 inches long. To forestall splitting the jamb trim, predrill those screw holes.