The obvious purpose of any lock is to keep unwanted people out, but the kind of lock you buy depends on where it's going in the house and your budget.
Exterior doors. To be truly secure, any exterior door needs a deadbolt. You have a choice of separates—a deadbolt and a lockset mounted separately—or a handle set that incorporates both features. Prices vary from $25 to over $300, reflecting a wide range of quality and style. Higher-end units typically feature solid, forged-brass components and a Grade 2 or even a Grade 1 (commercial duty) security rating. An antitheft option you should look for on locksets or handle sets is a dead-locking latch bolt; it prevents burglars from jimmying the latch with a credit card. On dead bolts, look for hardened pins that can withstand sawing. And because a latch or bolt is only as strong as the strike plate it engages, make sure the lock you're considering comes with a heavy-duty plate and 3-in. screws.
A handle set that allows you to open both the dead bolt and latch from inside with a single motion is convenient and could be a lifesaver in an emergency. Another terrific convenience is universal keying, which allows you to carry one house key despite having installed locks on other doors from different makers. As for esthetics, look for dual-torque springs that prevent knobs from sagging and a no-tarnish lifetime finish.
Keyed-Entry and Handle Sets
Where they go: Keyed-entry locksets, also called cylindrical and exterior-door locksets, are lever or doorknob units installed in exterior doors that are meant to work in tandem with a dead bolt. Handle sets are locksets with doorknobs or lever handles inside and swan's necktype handles outside. Handle sets always include a dead bolt. Look for models where the lock and dead bolt are interconnected so you can unlock both with a single motion in case of an emergency exit.
Features to look for:
• A Grade 2 security rating.
• A dead-locking latch bolt, or dead latch. This small rod adjacent to the strike that protrudes into the adjacent doorjamb prevents the lock from being jimmied with a credit card.
• An emergency-exit feature that allows the inside knob to turn freely to open the door, even when it's locked.
• A six-pin keying system. It costs more than a five-pin keying system, but is harder to pick.
• A heavy-duty-steel or -brass strike plate. Screws securing it should be 3 in. long and penetrate the framing behind the jamb.
• Dual-torque springs to keep knobs from sagging or loosening with age.
• A protective shroud behind the rose (the decorative circular collar mounted flush to the door). The shroud shields the lock mechanism even if the rose is pried off.
• Universal keying, which allows a single key to operate locks from different manufacturers.
• A tarnish-free finish and mechanical warranty (both lifetime).
Where they go: On exterior doors, typically 6 to 12 in. above the keyed entry (locking door handle) or handle set (handle and dead bolt combination) for added security. Double-cylinder dead bolts require keys to open the lock from the interior as well as the exterior. This makes it more secure—burglars can't unlock the door by breaking door glazing or a sidelight and reaching in—but it can be very dangerous if there's a fire and you need to make a fast exit in smoky, poor-visibility conditions. Proponents suggest hiding a key nearby, but building codes in many areas require single-cylinder units that have a turnpiece on the inside.
Features to look for:
• For most homes, a Grade 2 rating. Grade 1, a commercial rating, offers added security—at added cost. Avoid Grade 3. And beware of ads touting dead bolts with "Grade 1 features." The rating must be for the entire lock.
• A forged, solid-brass plug (the part that the key turns) and cylinder (the part that surrounds the plug). Avoid less expensive locks that have softer brass-plated zinc cylinders and plugs.
• A six-pin keying system, which is harder to pick than a five-pin system.
• A heavy-gauge-steel or -brass strike plate. Secure it with 3-in.-long screws that go through the jamb into the framing.
• A 1-in. throw, which means the bolt extends a full 1 in. into the jamb.
• A free-spinning, sawproof, hardened-steel pin at the center of the bolt. If thieves use a saw on the bolt, the steel will resist the blade and the pin will spin, frustrating the cutting action of the saw.
• A housing that protrudes into the door face rather than one that sits flush with it. This prevents thieves from sheering the dead bolt off with repeated hammer blows.
• Large turnpieces on the interior side that offer more leverage for children or anyone else who has difficulty opening dead bolts. Look for Americans With Disabilities Act (ADA) compliance.
Installing Locksets and Dead Bolts
1. POSITION THE TEMPLATE. Most doorknobs are 34 to 38 in. high, with dead bolts 6 to 12 in. above that. Decide for yourself what height is comfortable. When drilling new holes, tape the manufacturer's template in place with the lockset centerline at the desired height. Determine the backset—the distance from the door edge to the knob centerline—and use the corresponding template marks. The backset can be 2 3/8 or 2 3/4 in.; many locksets accommodate both. Then drill 1/8-in. pilot holes through the door to center the 2 1/8-in. hole saw. At the door edge, use the template to drill a 2-in.-deep pilot hole for drilling for the strike or bolt.
2. DRILL THE DOOR face and mark the jamb. Using a drill with a bubble level or a torpedo level taped on top, drill halfway through the door from each side with the hole saw to prevent blowout splintering. Then mark the doorjamb for the strike plate by closing the door, inserting a nail from inside the 2 1/8-in. hole through the strike pilot hole and pushing it into the jamb.
3. DRILL THE JAMB and door edge. With the nail mark as an indicator, drill a 5/8-in.-deep hole for the strike or a 1-in.-deep hole for the dead bolt using the 1-in. spade bit (sizes vary, so check instructions). In the door edge, use the pilot hole to guide a 1-in. spade bit and drill through to the large hole where the cylinder will sit.
4. CHISEL THE JAMB and door edge. Hold the latch assembly up to the door edge and score its outline deeply with a utility knife. Do the same for the strike plate on the doorjamb. Then score the wood to be removed at 1/4-in. intervals with a chisel, removing enough wood so the strike box sits flush with the door edge and the strike plate sits flush with the doorjamb.
5. INSTALL THE HARDWARE. Insert the latch assembly in the hole you drilled in the door edge and fasten it with screws after predrilling for them. Next, insert the handle set and cylindrical lock or dead bolt assembly so the spindle or tailpiece aligns with the strike assembly. Typically, screws pass through the door to hold the two lockset pieces together on opposite sides. For security, be sure exposed screwheads are on the interior side of the lockset.