Step-by-Step

With a straightedge clamped in position, use a sharp utility knife to cut through the veneer about 1/16 inch above where you want your final cut. It may take several passes with your knife to do this. Move and clamp the straightedge into final position and complete the cut with a circular saw (see Using a Miter Box, Related Projects).

If you cut off more than about an inch of a hollow-core door, the door will be hollow at the place you just cut. Clear out some of the cardboard webbing with a chisel. Rip a piece of softwood to the required width and length. Apply white glue to both sides of the piece and tap it into position. Clamp firmly until the glue is set.