Two general kinds of locksets are available for doors: cylindrical and mortise. A cylindrical lockset fits into a large hole bored into the door’s face; a mortise lockset fits into a rectangular pocket cut into the door’s edge.
Exterior doors may have either cylindrical or mortise locksets. Interior doors usually have a cylindrical lockset operated with a push button, though some older homes may have interior mortise locksets. Exterior cylindrical locksets are operated by a key inserted into the exterior knob; the interior knob is operated either by a small push or turn button on the knob or by a key. An exterior mortise lockset normally has a deadbolt that is an integrated part of the locking mechanism—when you turn the key from outside, it releases both the knob and the deadbolt.
If you are concerned about security, be sure your exterior doors are protected by deadbolts with a minimum 1-inch "throw."
Keeping moving parts clean and well lubricated will prevent most lockset problems. Others can be prevented by correcting any warped or sagging doors promptly.
Problems with locksets usually affect either the latch assembly or the lock mechanism. A latch problem may be the result of a door that fits poorly. A lock mechanism problem may be caused by a dirty or unlubricated lock. More complicated lock problems may call for a locksmith or replacing a lock. If a lockset needs to be replaced, be sure to buy one of the same type and size.
