The two most popular standard locksets are the tubular locks and cylindrical locks. In design, both look about the same. The lock is on the inside of the door so that if a child locks the door and can't get out, you can activate the lock by sticking a nail or stiff piece of wire into a small hole in the knob of the lockset on the outside of the door. Similar passage locksets, often used on closets, do not have a locking device, just a latch system that keeps the door latched in a shut position. You just turn the knob to move the latch.
Tubular locks are less expensive than other type residential locks.
They are usually packaged with installation instructions and provide templates for cutting the necessary holes in the door. Cylindrical locks are made for exterior or entrance doors and commercial installations that demand better privacy. They are heavier and stronger than tubular locks. For security reasons, the lockset is mounted from the inside of the door so that no screws are available for bad guys to disassemble as a means of gaining entrance. Deadlocks or deadbolts are a 2-hole locking assembly.