How to Fix Hollow Doors Cut Too Short

Lay the shortened door across a pair of sawhorses and then saw off an extremely small portion of wood from the rail on the side of the door you want to make longer. Generally speaking, this is the bottom of the door. Since this is a hollow door, saw the front and back rails of the door. Cutting exposes fresher wood, a surface more conducive for gluing. Use some fine sandpaper -- 220 grit is recommended -- to remove any burrs so that the rails are relatively smooth.

Hang the door back into the jamb -- don’t screw in the hinges, just set the door in the frame -- and slide shims under the bottom rails of the door to raise the doorknob to the desired height. Reverse the process if you’ve cut from the top of the door -- hold the door in the jamb and shim the top of the door. Once the door is straight, measure from the rail to the bottom of the doorframe and then measure the right and left side gaps with a tape measure or ruler.

Measure and cut two filler strips made from wood that’s no more than 1/4 inch thicker than the door itself. Also, cut one of the sides of both filler strips to be equal to the biggest gap you measured on the door -- either the right or left side, as stated in Step 2 -- and no more than 1/4 inch longer than the width of the door. Drill pilot holes into the filler strips, one on the left side and one on the right side of each strip.

Place the door back onto the sawhorses, generously apply wood crafter’s glue along both the door rails and backsides of each filler strip and press the strips across the rails. C-clamp the strips in place and screw holding screws into each of the pilot holes. Allow ample time for the glue to dry.

Sand the raised filler strips down until their surfaces are even with that of the door. Remove the holding screws; the strips should be firmly in place and ready to paint or stain prior to hanging the door as you normally would.