Porcelain cylindrical locks------Privacy Locks & Single 

Privacy Locks ---Usually used on bathroom doors, and any other door that needs to be locked from the inside. A push button is provided on the inside rosette, pushing the button fixes the outside handle, turning the inside handle releases the lock. A clearance hole is provided in the outside rosette to permit the lock to be released with a nail, if needed. 

Single Cylinder Locks---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.