Cylinder Lock Options

Single Cylinder vs Double Cylinder Locks

The cylinder is the locking mechanism of an entry door set. It may be integrated with a the deadbolt of a mortise lock or mounted independently as part of a separate deadbolt. There are two types of cylinder locks commonly used for residential applications. A "single" cylinder lock is operated from the outside with a key, and from inside with thumb-turn. One can secure the door from inside, as well as exit the house without a key, making this the most popular option. A "double" cylinder lock is operated with a key from both inside and outside. While such locks provide added security for doors with glass panels or sidelights, they prevent egress without a key. For this reason, double cylinder locks are not residential code compliant in some locales.

Single Cylinder Lock: Key operated from the outside, thumb-turn operated from the inside.
Double Cylinder Lock: Key operated from both inside and outside. Note: Key required for egress.