BACKSET
In the U.S. there are two common backsets for residential door locks, 2-3/8" and 2-3/4". The backset is the distance from the edge of the door to the center of the 2-1/8" bore hole.

DOOR PREPARATION
Locks fit into a standard American style tubular door prep. If you are replacing existing locks then your door preps will most likely be correct for standard locks. Just determine the backset and you're ready to order. If you're installing locks in new doors that do not have a door prep you can follow the instructions below.