How to Set Interior Doors

Lay a level in the doorway to check if the floor is level. If the hinge side sits lower than the latch side, slide wooden shims underneath the level's low end until it matches the high end's height. Do not use shims to raise a lower latch side.

Lift the prehung door into the opening. Hold a level against the door's hinge-side jamb. Place wooden shims behind the hinges to straighten the door jamb. Use a pneumatic nailer to hammer finishing nails through the jamb and shims to hold the door in place.

Close the door. Measure the gap between the door's top edge and the upper jamb's bottom edge. The gap should be even all the way across. Adjust the latch jamb up or down to even out the gap.

Hold a level against the latch jamb. Slide wooden shims between the jamb and the opening to straighten the jamb. Place the shims at approximately the same locations as the shims on the door's hinge jamb. Use a pneumatic nail gun to drive finishing nails through the jamb and shims to hold the door in place.

Insert shims between the latch jamb and the rough opening, near the door's top edge. Use a pneumatic nail gun and finishing nails to secure the jamb and shims in place. Insert more shims between the latch jamb and the rough opening, near the door's bottom edge. Secure these in place with finishing nails. These shims prevent the door jamb from flexing.

Use a utility knife to score each shim at the point where it sticks past the door jambs. Bend the shim back and forth along this line to break it off.