The deadbolt lock work by effectively bolting the door into its frame. The bolt is “dead” in that it has to be manually moved in and out of place by means of a key or knob. There are three basic parts of deadbolt lock: a key-accessible outside cylinder, the “throw” (or bolt) which slides in and out of the door jamb, and the thumb-turn, which allows for manual control of the bolt from the inside of the home. A standard horizontal throw extends one inch beyond the edge of the door and into the jamb. All deadbolt locks should be made of solid steel, bronze, or brass; die-cast materials are not fashioned for great impact and could break apart.
The principal weakness of any horizontal deadbolt lock is that it is possible for an intruder to pry the door apart from the jamb or its strike plate in the jamb to disengage the throw. This can be remedied with a vertical (or surface-mounted) deadbolt, which resists the separation of lock from jamb. The throw of a vertical deadbolt engages by interlocking with a set of cast metal rings affixed to the frame of the door. The rings surrounding the bolt make this lock essentially pry-proof.
In the instance of a door containing glass panes, a double-cylinder deadbolt might be employed. This particular type of deadbolt lock requires a key to unlock the bolt from both the outside and inside of the home – so a potential thief cannot simply break through the glass, reach inside, and manually unlatch the thumb-turn in order to unlock the door. However, some fire safety and building codes forbid the installation of locks that require keys to open from the inside, so consult with a contractor or locksmith in your area before installing one. Consider alternatives to the potentially hazardous double cylinder deadbolt. Try installing a supplemental lock that is completely out of arm’s reach (either at the top or flush to the bottom of a door); security glazing; or impact-resistant glass panels.
It’s important to remember that no lock is 100 percent guaranteed to deter or keep out all intruders. However, you can greatly reduce the likelihood of intruders by making sure that all exterior doors are fitted with some form of deadbolt locks and strike plates, and that you are diligent in using these locks while at home and away.