How to Mortise a Door Jamb

Mortising a door and door jamb for the hinges and strike plate often comes along with the job of replacing an old door.

The strike plate is a flat piece of metal which curves on one side. It is installed on the door jamb at the same height as the door latch. The latch rests inside the strike plate to hold the door closed. Strike plates are mortised, or sunk, into the door jamb, allowing the door to open and close without rubbing.

Close the door. With a pencil, place a light mark onto the door jamb's edge, indicating the center of the latch. Open the door. Align a small level with the mark you just made and draw a line across the side of the jamb.

Drill out the strike plate's inset using a 7/8-inch spade bit. First, drill the bit 5/8 inches into the door jamb slightly above the mark. Then move the drill bit down so that the two circles will overlap each other slightly. Drill another 5/8-inch-deep circle.

Place a chisel's edge against one of the points inside the two circles. Tap the back of the chisel with a hammer to drive it through the point, removing it. Repeat with the point on the opposite side.

Place the strike plate onto the door jamb with the curved end facing in the direction the door opens. Line up the strike plate's hole with the mortise you just made in the door jamb. Trace around the strike plate with a utility knife. Set the strike plate aside.

Tap the chisel's edge into the door jamb, following the outline of the strike plate. Push the edge into the wood as deep as the strike plate's thickness. Angle the chisel into the outlined area. Tap the back of the chisel with a hammer to drive it through the wood, removing it. Place the strike plate into the mortised area to ensure that it sits flat with the surface of the door jamb.

Drill pilot holes through the strike plate's two screw holes using a 3/32-inch drill bit. Secure the strike plate to the door jamb using the provided screws.

Things You Will Need

  • Pencil
  • Level
  • Drill
  • 7/8-inch spade bit
  • Chisel
  • Hammer
  • Utility knife
  • 3/32-inch drill bit
  • Screwdriver

Tip

  • If you cut the mortise too deep, cut a thin piece of cardboard and fit it behind the strike plate to bring it forward.