How To Choose a Deadbolt Lock
Deadbolt locks add greater security to a door than a standard lockset. A standard lockset has a locking doorknob that prevents the latch from being retracted when the door is locked. However, it does not offer much resistance against force. If a door with standard lockset is kicked-in, the latch, which penetrates only about 3/4" into the door jamb, will cause the door jamb to splinter and the door will swing open.
A dead bolt lock is designed to slide a heavy steel bolt into the door jamb. Some bolts are 1 1/2" long or more and these longer bolts resist more force. With the use of extra long screws in the latch plate, a good deadbolt lock can resist repeated kicks.
Deadbolt locks are commonly available as single cylinder or dual cylinder models. A single cylinder has a keyed lock on the outside and a finger latch on the inside. A dual cylinder has a keyed lock on both sides. Dual cylinder locks are typically used on doors with glass in them or nearby. Nearby glass can be broken and an intruder can reach inside to unlock a single cylinder deadbolt. However, dual cylinder locks are not legal in all communities because they pose a safety hazard to the occupants of the residence. In the event of an emergency, such as a fire, could you find the key, possibly in the dark, and unlock the door? Could every member of your family?
The quality of the lock does matter. Some models are more easily picked or simply broken. Look for a model with a long bolt and the bolt should be made with hardened steel. If it comes with only 3/4" or 1" screws for the jamb plate, purchase screws of 3" or 4" to replace them. The shorter screws should only be used on the assembly mounted in the door. Use the long screws in the door jamb.
A deadbolt lock with a long bolt of at least 1 1/2", and 2 1/2" + screws holding the latch plate will greatly improve the security of most exterior doors. Deadbolt locks are not complicated to install yourself or a professional can install one for a modest fee.