How to Hinge Mortise a Slab Door

Stand the door slab upright on its long edge, with the hinge edge facing upward. The door can be braced against a sawhorse or workbench to hold it firmly during the hinge mortising.

Mark the location centerline for each hinge you will install on the door slab. Interior doors, which are usually lighter, hollow-core slabs, typically utilize two hinges, one positioned 10 to 12 inches down from the top and the other 12 to 16 inches up from the bottom. Exterior doors, commonly heavier solid wood slabs, are fitted with three hinges. Two use the same positioning, while the additional hinge is centered between the other two.

Remove the pin from a door hinge to separate the two leaves of the hinge.

Align the door-side hinge leaf on a centerline marked in Step 2, and trace the outline of the perimeter on the door edge. The hinge leaf with the largest number of pin loops is the door-side leaf.

Score the hinge leaf outline, using the tip of a utility knife. Cut the scored line approximately 1/8-inch deep.

Mortise out the hinge space, using a wood chisel. Slide the chisel parallel with the wood grain, working slowly to control the tool. Work the mortise cut up to the scored perimeter line, being careful to cut cleanly along the edge. The scoring can be "refreshed" using the utility knife, if needed. Continue to test the mortise depth using the hinge leaf, to prevent cutting the mortise too deep. The finished mortise should hold the surface of the hinge leaf just flush with the door edge's surface.

Repeat Steps 4 through 6 to cut the remaining hinge mortises in the door slab.