Backset is a term related to the way a door is prepped for lock installation. It refers to the distance between the edge of the door and the center of the door hardware. Most residential doors have a backset of 2-3/8” and most commercial doors use a slightly longer backset of 2-3/4”. These are not hardfast rules. Though some hardware is adjustable for either backset, it’s not always the case and sometimes you need to consider backset when ordering new locks.

Back in the ‘60s and early ‘70s they thought it was cute to install locks with a 5” backset. Nowadays that creates a bit of a problem when the locks fail because you can’t just walk into Home Depot and buy a lock made for one of these oddly prepped doors from the 1960s. In those days, houses were rarely secured with anything more than locking doorknobs, so it also presents an issue when you want to add a deadbolt to the door. You have to decide whether to install a deadbolt that’s out of alignment with the knob, or to find one with an extended latchbolt. If you take the latter route it will always be a hassle to service or replace the lock. I usually advocate for the offset.

Here’s a case where someone decided to give up on looking for the specialty hardware. Instead he just installed a new deadbolt with a standard backset right next to the lock with the longer backset.