How to Make an Inset for a Door

Measure the opening in your door using a tape measure. Insert a framing square into each corner to ensure the opening is square. Note any irregularities, along with the width and height of the opening.

Cut four lengths of wood molding at 45-degree angles, using a miter saw and miter box. Cut the molding to length by applying the dimensions of the door opening to the outside edge, or the edge opposite the molding's rabbet. For example, if the door opening is 12 by 24 inches, cut two pieces of molding 24 inches long on their longest sides and two that are 12 inches on their longest sides.

Apply wood glue to the ends of two dissimilar pieces of molding. Secure them together in a joining vise or with clamps. Insert a framing square into the corner of the two pieces of molding form to ensure they join squarely. Make small adjustments to the vise or clamps as necessary.

Insert a 1-inch finishing nail into the end of each joined length of molding. Stagger them slightly so the second nail doesn't contact the first nail inside the wood.

Allow the glue to set overnight or based on the manufacturer's directions. Remove the clamps or take the molding out of the vise.

Repeat steps 3 through 5 to make two L-shaped corners. Join the remaining two corners using the same procedure to produce a square or rectangular inset frame.

Insert the inset material from behind into the rabbet that forms the inner edge of the inset frame. Measure the size of the opening, including the width of the rabbet, using the tape measure.

Cut four pieces of small molding to fit inside the rabbet to hold the inset material in place. Use a miter saw to create 45-degree angles. Join the molding with the same process you used for the inset frame.

Insert the small molding into the rabbet on top of the inset material. Secure it by hammering 1/2-inch finishing nails through the molding at an angle every 6 inches. Angle the nails so they drive into the inset frame but not through the inset material.

Place the finished inset into the door opening. Plane down any edges or corners that prevent it from fitting, using the wood plane. Make one stroke at a time with the plane before reinserting the inset to check its fit. Sand the edges with medium-grit sandpaper if it looks like another plane stroke would remove too much material.

Attach the inset to the door once it's the right size. Drive 1-inch finishing nails through its edges at 6-inch intervals. Angle them so they drive into the door.