The deadbolt lock has a bolt that must be activated by a key or thumb turn. It offers good security because it is not spring activated and cannot be “jimmied” opened with a knife blade or credit card. For this reason it is best to install deadbolt locks on solid wood, steel or fiberglass doors. These doors resist forced entry because they are not easily battered or bored.
A single cylinder deadbolt is activated with a key on the exterior side of the door and a thumb turn piece on the interior side. Double cylinder deadbolt locks can hinder escape from a burning home so always leave a key in or near the lock when someone is home. Double cylinder deadbolt locks are only permitted in existing single-family homes, town homes and first floor duplexes used exclusively as residential dwellings.