What is a backset?
The Backset is the distance from the edge of the door to the center line of the prep in the door. In the U.S. there are two common backsets for residential door locks, 2-3/8″ and 2-3/4″. Dummy sets have no latch and are surface mounted so you can install a dummy set wherever you choose on the door.
Backset is the distance measured from the edge of a door to the center of the cross-bore in the door face where the lock will go through. Typically you can measure to the key hole of an existing lock. On doors with a bevel or radius, measure from both sides and average the distances to get an accurate reading. You can view a diagram.
