The majority of interior doors are prepped with a single bore hole, which is a large diameter hole where the door knob is mounted. Bore holes are typically 2 ⅛” in diameter. There is also a 1" cross bore that extends from the door edge through the bore hole in order to install the latch.
Standard door preparation isn’t unnecessarily complicated, but if you get the holes in the wrong place when you’re boring or mortising a door for a knob or lock, it’s a hard mistake to fix. It may even be necessary to buy a new door.
Fortunately, you can easily get the holes right if you pay attention to two key dimensions and use the door's paper layout template. In this blog, the team at Access Residential Hardware goes over the key steps involved in standard door preparation, along with the tools you’ll need and how to make a template if yours is lost or damaged.
To make the holes, you need a 2 ⅛” hole saw and a 1” spade bit. With some deadbolts, you’ll need a 1 ½” hole saw instead, so read the instructions carefully to make sure that you have the right tools.
Key Dimensions You will Need
Door thickness is the first key dimension you need to know. Interior doors are usually 1 ⅜” thick, while exterior ones tend to be 1 ¾” thick. Mark the door for boring with the mark on the template that corresponds to its thickness.
Pro Tip: You'll probably need a special-order lock if your door is thinner than 1 ⅜” or thicker than 1 ¾”.
The second important dimension is the backset, which refers to the distance between the center of the knob or deadbolt and the edge of the door. The majority of doors have a 2 ⅜” or 2 ¾” backset, and most modern deadbolts and locksets are compatible with both.
The 2 ¾” backset is generally preferred because it leaves more room for your knuckles when the door is being closed. A 2 ⅜” backset, however, looks better on narrow doors and those with narrow stiles, such as full-glass doors.
Step #1: Tape on the Template
Attach the template to the door with painter's tape and mark the center of the cross bore with a scratch awl or nail. Based on the thickness of the door, mark the center of the edge-bore hole. The marks must be deep enough so that the pilot bit on the hole saw will not move when you start the drill.
Step #2: Drill the Cross Bore
Drill about 1” deep using a 2 ⅛” hole saw or a 1 ½” hole saw (refer to the lock instructions). Use the pilot hole to register the hole for drilling from the other side after removing the hole saw. Be sure to maintain a firm grip on the drill and keep the bit level.
Step #3: Drill the Edge Bore
For the diameter of the edge bore, refer to the manufacturer's instructions. Strike assemblies typically require a 1” hole. For wood edges, use a spade bit, and for metal edges, use a hole saw. To ensure smooth operation of the bolt, keep the bit level and straight.
Step #4: Mark the Mortise
The bolt assembly should be inserted into the door edge and temporarily screwed in place. With a utility knife, mark the shape on the door's edge. To avoid marring the door, make several light passes with the knife. Then take out the bolt assembly.
Step #5: Chisel the Mortise
Cut the mortise for the bolt assembly with a sharp ½” chisel. By working from the edges toward the hole, you will avoid slipping and ruining the door's edge. Gradually work your way up the mortise, taking shallow passes and maintaining a level bottom. The mortise should be deepened until the bolt fits flush with the door edge.
Step #6: Secure the Bolt
Install the screws that secure the deadbolt to the door's edge using the screw holes made earlier. Screw heads are less likely to be damaged or stripped with a conventional screwdriver than with a cordless drill or impact driver.
Step #7: Install the Lock Assembly
Make sure the lock is oriented properly and right side up. Align the parts so they correspond with the correct backset (2 ⅜” or 2 ¾”). Drive in the long screws that attach the two halves of the assembly.
Step #8: Identify the Strike
Put chalk powder on the end of the bolt. Operate the lock while holding the door shut in order to transfer the bolt location to the jamb. Follow the mark on the strike plate to trace the hole in the middle of the stroke.
Step #9: Drill the Jamb
For the lock bolt, drill a hole through the jamb using a 1" spade bit. Check the lock operation after closing the door. Expand the hole with a small chisel or round file if the lock is difficult to turn or doesn't engage fully.
Step #10: Install the Strike
Temporarily fix the strike plate in place, and then trace the strike with a utility knife. Mortise the recess with a ½” chisel after removing the strike. To prevent break-ins, use the provided 3" screws.
Did You Lose Your Template?
Hardware stores sell templates, but they generally only allow you to drill one borehole at a time. For a door handle and keyed deadbolt, you may want to build your own template so the holes are precisely spaced.
Start by getting a piece of ¾” thick plywood 18" wide and 8" high. Then draw a line 3/4" from the edge. You can measure over that line for your backset (2 ⅜” or 2 ¾”) and space them vertically at 5 ½” cc. In each center point, drill a hole 2 ⅛” in diameter. The same process can then be repeated on another piece of plywood of the same dimensions.
Pro Tip: It will be easier to line up things on the door if you place the bottom bore hole exactly 6" from the bottom of the template.
Finally, you’ll want to cut a strip of plywood the same width as your door: 1 ⅜” or 1 ¾”. To mark the locations of the cross bores, line up the measurement lines with the side pieces. The cross bores should be 1" in diameter and aligned exactly with the 5 1/2" cc bores you made before. After you've prepared that piece, screw the 3 pieces together into a U shape and clamp the template to the door.
Standard Door Preparation for Latches
In addition to the cross bores, a door can be prepared for three different kinds of latches.
The easiest latches to install are drive-in latches. A door prepared for a drive-in latch has a 1" cross bore on the edge. All you have to do to install the latch is slide it into the cross bore and tap it gently into place. When the drive-in latch is driven into the door, the ridges around the top hold it tightly in place.
Rounded Corner Faceplate Latches
Faceplate latches with rounded corners are very common. The faceplates measure 2 ¼” high and 1" wide, with a ⅛” radius around the corners. A door supplier will typically use a router jig to prepare the door so that all you have to do is install the latch. Alternatively, if your doors are not prepared this way, but you still want a faceplate, you can buy locks with square corner faces since they can be chiseled out more easily.
Square Corner Faceplate Latches
A 1" chisel can easily make your door ready for faceplates if your door is prepped for drive-in latches. The area should be 1" wide by 2 ¼” tall and chiseled about ⅛” deep. A square corner faceplate gives your door a clean and elegant appearance.
Access Residential Hardware Has the Door Hardware You Need
Once standard door preparation is complete, it’s time to locate a trusted provider of quality door hardware. At Access Residential Hardware, we sell exterior door hardware and interior door hardware from leading manufacturers like Schlage, Emtek, and Baldwin. No matter how your home is decorated inside and out, we have knobs, levers, and sets that complement the overall theme. To see what we have in stock at any time, please visit our product pages and if we can help you further, call 866.752.9002, or fill out this contact form.