There are a few things you need to know to order the correct hardware for your door. First, check out the image below and see where the “backset” and the “square corner latch prep” are located. These are the key things you’ll need to know to order the correct hardware for your door.

The backset is the distance between the leading edge of your door and the center of the “borehole,” which is where the handle or deadbolt is mounted on the door. There are two standard backset measurements for US doors: 2-3/8” and 2-3/4”. You can determine which of these you have with the current door handle or deadbolt installed (measure from the door edge to the keyhole, which is the center), although we recommend removing the hardware and measuring the backset of the borehole itself without the hardware installed. It’s easier to be sure of your measurement when you don’t have to deal with a lock or handle projecting from the door.

Next, you’ll need to identify whether your latch prep is a square corner (as seen on the drawing) or radius corner, which just means that the corners are rounded instead of sharp, 90-degree angles. This is where the latch (the tubular piece of the lock that actually sticks out of the edge of the door) goes. Occasionally you’ll encounter a door without a latch faceplate cut into the edge of the door: In this case you would use a drive-in latch, and you won’t need a latch faceplate. Once you’ve identified these details, you’re ready to order your hardware!