Purchase Door and Hardware
Purchase the new doors and hardware, after determining the correct size and design, and assemble your tools. The homeowner in this project selects six-panel solid pine doors, so called because they have six decorative beveled panels. Each door will require installation of the lockset and latch mechanism, and three hinges with components on the door itself and on the doorframe.

Remove Hinge Pins
Tap upward with a hammer and flathead screwdriver under the heads of the three hinge pins on the first old door to disengage the pins from the hinge knuckles. Have a helper support the door to prevent its weight from binding the pins. Remove them completely.

Remove Door
Lift the door slightly and then pull away from the doorframe to disengage the hinge knuckles.

Remove Old Hardware
Unscrew the mounting screws with a power driver/drill and remove all the old hardware from the door and doorframe.

Lay Old Door on Top of New Door
Lay the old door flat on top of the new pine door and support them with sawhorses to make a more convenient work surface. Note that the new six-panel door is only symmetrical from left to right, not from top to bottom. It has two long pairs of beveled panels and one short pair at the top, so be sure to orient the top of the old door to the top of the new door.

Align and Clamp Doors
Align the doors so that the edges are flush at the hinge edge and clamp them together. If they are not exactly the same size, put all the excess on the doorknob side. You will plane that surface in a later step to ensure that the edges are even.

Score New Door with Utility Knife
Use the old door, which fit well in its doorframe and latched properly, as a template to transfer the positions of hinge mortises and holes for the lockset components to the new door. Align a combination square precisely along each narrow edge of the hinge mortise in the old door and score the new door with a utility knife to mark the line. Marking with a knife, rather than marking with a pencil, makes a more exact mark/scribe.

Measure and Score a Line for the Mortise
Measure and score a line for the side of the mortise that has a margin between it and the edge of the door. The opposite side of the hinge mortise will be flush with the edge of the door and does not need a mark. Be sure to maintain the same orientation and position for the new mortises. (You do not want to create a reverse image for the mortise.) Repeat steps 7 and 8 for each hinge to mark its mortise.

Create a Jig
Use clamps and two-by-sixes to create a jig to hold and brace the door on edge. With the doorknob edge upward, we note that the new door is about 1/8 inch wider than the old door.

Shave 1/8-inch off the Edge of the Door
Use a power plane to shave the 1/8 inch off the edge of the new door. The process should only take a couple of light passes with the planer, because the difference in size is so slight.

Cut a Hole for the Lock Cylinder
Return the clamped doors to the saw horses (flat with the old door on top) and use an arbored hole saw on your power drill to cut/bore a hole for the lock cylinder. Again, use the hole in the old door as a template. Its thickness will help support the hole saw and drill, holding them vertical. Bore just far enough for the pilot bit on the hole saw to come through the other side of the new door.

Finish Making Cutout for the Lock Cylinder
Flip the clamped doors over and re-insert the pilot bit in the hole to finish making the cutout for the lock cylinder. Hold your combination square at the edge of the drill to ensure that the hole saw is vertical while you cut. Cutting the hole from both sides ensures that the edges are smooth without any tear-out.

Bore a Hole for the Latch Bolt Assembly
Brace the door on edge again with the lock cylinder side upward and use a spade bit to bore the hole for the latch bolt assembly. The hole must be straight (vertical as you drill downward into the edge of the door), so hold your combination square at the side of the drill to ensure that you are holding the tool in a true vertical position.

Screw Latch Assembly in Place
Screw the latch assembly in place temporarily with a power driver/drill.

Scribe Around Outside
Scribe around the outside edge with a utility knife to mark the location of the plate and, ultimately, of the mortise you will cut.

Cut a Shallow Depth Along Perimeter of Latch Mortise
Set the chisel blade straight down into the knife score just made and tap it with a hammer to cut to a shallow but consistent depth along the entire perimeter of the latch mortise.

Remove Shallow Layer of Wood Across Surface of Mortise
Place the beveled side of the chisel blade downward at a fairly flat angle and tap it with a hammer to excise a shallow layer of wood across the surface of the mortise. The mortise needs to be just deep enough to receive the latch plate and hold it flush at the surface of the door.

Pare Off Wood to Make a Clean Smooth Surface
Turn the chisel blade so the beveled side is up and pare off enough of the wood to dress the mortise and make a clean smooth surface. Remember to hold the chisel at a shallow angle so that you do not make the mortise deeper.

Repeat Steps 16 through 18 for all Three Hinges
Flip and brace the door so that the hinged edge is up and repeat steps 16 through 18 for each of the three hinges. You already scribed the perimeters of the hinge mortises in an earlier step. Check one more time to ensure that the hinge mortises are correctly oriented before you chisel them.

Secure Hinges
Secure the hinges to the door with mounting screws.

Install Lockset Components
Install the doorknob and other components of the lockset, and secure them with screws.

Mount New Hardware
Mount the new hardware (hinges and the strike plate for the latch bolt assembly) into the doorframe, driving screws with the power driver.

Hang the Door
Hang the door. Engage the hinge knuckles on the door with those on the doorframe and slide in the hinge pins with the assistance of a helper to hold the door.

Tap With a Hammer
Tap gently with a hammer to ensure the pins seat fully in the hinge knuckles.

Test Door Latch
Test the door to ensure that it latches.