Single Cylinder
The most popular configuration for deadbolt locks, a keyed cylinder is provided for the outside and a turn-piece is located on the inside. The lock may be locked or unlocked with a key from the outside. The turn-piece allows locking or unlocking without a key from the inside.
Double Cylinder
Used in situations where free egress from the inside is not needed or desired. Keyed cylinders are provided for both outside and inside. Locking and unlocking can be accomplished only with a key.
