How to Reuse an Old Hinged Door as a Pocket Door

Measure the gap between the uprights forming the door pocket with a tape measure and choose a door that will fit comfortably into it. The door thickness should be at least 1/8 inch smaller than the gap.

Remove all the door hardware with a screwdriver, including the hinges, knob and deadbolt, if there is one.

Measure the distance from the rail on which the door slides to the floor. Cut the door about 1/2 inch shorter than this distance with a circular saw. If you have to cut off more than 1 inch, cut half of the amount you need from the top and half from the bottom. This will allow you to preserve the internal framing of the door if it has a hollow core or its symmetry if it is solid and has carved features or a window.

Lay the door on a pair or sawhorses and lay a sheet of wax paper over the knob hole, covering it completely. Screw a 4-by-4-inch piece of plywood to the door so it covers the wax paper and the hole. This will allow you to fill the hole from the other side.

Turn the door over. If it has a hollow core, stuff old newspaper around the edges of the knob hole and down into the gap between the two faces of the door. Omit this step if the door is solid.

Spray foam insulation into the hole until it is about half full. The foam will expand as it dries and bulge out of the hole. Cut it flush with a utility knife when it sets.

Mix auto body filler with the hardener that comes with it and spread the filler over the dried foam with a putty knife until it is flush with the surface of the door or slightly below it. Let it set until it is hard, then sand down any part of the patch that bulges out with 120-grit sandpaper.

Apply a coat of drywall joint compound over the patch with a putty knife, let it harden, then sand it flat. Apply a second coat, if desired. When you are done, turn the door over, remove the plywood and peel off the wax paper. Cover the foam with auto body filler and joint compound in the same way. Fill the screw holes with joint compound.

Fill the hole in the edge of the door for the doorknob barrel with auto body filler, let it dry, then smooth it by topping it with joint compound and sanding it. Fill the mortises for the hinges on the opposite edge of the door in the same way.

Spread primer on the patches with a paintbrush. When it dries, paint the door with latex or alkyd enamel.

Screw sliders to the top of the door and hang the door on the track. Adjust the sliders so that the door hangs straight, then make sure it slides freely into the pocket.