What is Standard Door Prep

Standard Door Prep for Door Knobs & Levers:

Most interior doors are prepped with a single boor hole. The standard sized bore hole is 2 1/8" in diameter. Through the edge of the door there is a 1" cross bore that extends from the edge of the door through the bore hole. (This cross bore is where the latch is installed).


In addition to the two cross bores, a door can be prepped for one of 3 different types of latches:

Drive-In Latches:

The easiest style to install, as it doesn't require screws. Simply slide the latch into the 1-inch predrilled cross bore hole and tap into place with a rubber mallet. The ribbed collar around the edge of the latch will hold it securely in place.

Radius Corner Latches:

Rounded corner faceplate latches are very common. The faceplates give the latch a quality look and hold the latch securely in the door. These faceplates are 2 1/4" in height and 1" wide with about an 1/8" radius on the corners. Many door shops will use a router jig to prep the door for you so that all you have to do is install the latch.

Square Corner Latches:

Square corner faceplates are the same size as the rounded corner, they just have square corners. If you want faceplates, but your door is prepped for drive in latches you can easily prep your door for these using a 1" chisel. Just mark the area 1" wide and 2 1/4" tall centered on the cross bore and chisel out about 1/8" depth of material. These square corner faceplates give your door a refined clean look. If your doors are prepped for radius corner faceplates, but you prefer square - just chisel out the very corner.


Standard Door Prep for Tubular Handlesets/ Knob & Lever Deadbolt Combinations:

Standard door preparation for a door with both a door knob/lever and a deadbolt or Tubular Handleset have two sets of bore holes and cross bores stacked on top of each other at 5 1/2" from center to center (like the diagram shown below) It should have the exact preparation for the deadbolt, as the knob below with a 2 1/8" diameter bore hole and 1" cross bore.