Coping with Inside Miters

The best technique for applying molding on an inside corner is called a coped joint. Cabinet-makers have used this joint to create great-looking inside corners for centuries. The technique involves cutting a profile on the end of the molding that fits like a puzzle piece against the adjoining piece (see above). 

To create the profile, cut a 45-degree miter on the end of the molding (Photo 1), just as you would if you were going to miter the joints. Then, use a coping saw with a fine-toothed blade to cut out the profile (Photo 2). Only the simplest moldings will allow you to complete the joint with one long cut. For abrupt direction changes, you’ll need to back out of the cut and approach it from a different angle. Use files to clean up the profiled edge and fine-tune the fit (Photo 3). 

Photo 1: Make an inside 45-degree cut to create a profiled edge. The molding should be held upside down on the saw. A stop block clamped to the saw holds the molding in place.

Photo 2: Cut the profile with a coping saw following the profile line created by the miter cut. Angle the saw back about 30 degrees as you cut along the profile to remove more wood from the back of the molding. 

Photo 3: Files fine-tune the cut. Choose a file that matches the particular profile. File and test-fit until the joint is tight.