Increased Security Is Just a Deadbolt Away : SAFETY

Installing a deadbolt lock, or deadbolt--a solid steel bolt that operates independently from a doorknob--adds an extra measure of security to a home.

Beginning carpenters usually can install a deadbolt on a wooden door; moderate to expert skills are needed if the door is steel.

Buy a deadbolt lock with a bolt that will extend an inch or more from the door’s edge into the door frame. Deadbolts have one or two lock cylinders; a two-cylinder model requires unlocking with a key on both sides.

In a door with glass panels it prevents a burglar from reaching through a broken pane to unlock the door. But because it hinders quick emergency exits, some local codes prohibit its use.

Deadbolt lock kits come with all the parts needed. Included is a paper or cardboard pattern called a template, which serves as a guide for drilling the required holes in the door.

Follow the instructions that come with the kit. In most cases, start by attaching the template to the edge of the door at least six inches above the doorknob, then prick the template with an awl or nail to mark the holes.

Next, use an electric drill with a hole-saw attachment to bore a large hole through the door for the cylinder assembly, which passes from one side of the door to the other. A hole saw resembles a metal cup with a serrated rim.

To use, drill a pilot hole through the door with an ordinary one-eighth-inch-diameter drill bit. Then drill halfway through the door with the hole saw; withdraw the tool and finish drilling from the other side. This technique prevents splintering.

Wedge the door open and drill a smaller hole into the edge for the bolt, using a flat spade bit.

Both holes in the door must be precisely horizontal, and the hole in the edge must meet the larger hole at a right angle. The best way to ensure accurate drilling is to use a drilling guide, available at hardware stores. The guide attaches to the drill and holds the tool against the work at any desired angle.

Slide the bolt and attached mounting plate into the hole in the door’s edge and trace around the plate with a sharp pencil. Remove the bolt and carefully chisel away a thin layer of wood from inside the marked lines so the plate will lie flush with the surface. Then reinsert the bolt and fasten it to the door with the screws supplied.

Install the cylinder assembly by fitting each half against the opposite sides of the larger hole. The pieces meet in the center and capture the inserted end of the bolt. Long screws fasten the assembly.

Retract the bolt, dab the end with lipstick or chalk, then close the door and turn the lock so the bolt leaves a mark on the door frame. Drill a hole for the bolt into the frame, centered on the mark. Place the metal strike plate supplied with the kit around the hole.

Trace the plate’s outline, then chisel wood from the frame to fit the plate as you did installing the bolt.

For greater protection against break-ins, install a metal strike box instead of a strike plate. A strike box fits into the bolt hole, strengthening the door frame. Minor chiseling usually is required to enlarge the bolt hole so the box will fit. When mounting a strike plate or a strike box, use three-inch-long screws.