Coping is a technique for cutting inside corners that produces a much tighter joint than a simple miter. Instead of cutting both pieces at 45 degrees and hoping they meet perfectly, coping involves cutting one piece to follow the profile of the other, creating a joint that fits snugly even if the corner is not perfectly square.
Most walls do not meet at a perfect 90-degree angle. A mitered inside corner on shoe molding can look fine initially but often opens up over time as the wood dries and the house settles. A coped joint solves this problem because the shaped end of one piece butts tightly against the face of the other, hiding any small gaps caused by imperfect wall angles.
Cut the first piece of shoe molding square (straight across) on both ends. Push it tightly into the corner and nail it in place. This is the piece the coped end of the second piece will butt against.
Cut the second piece with an inside 45-degree miter. This back-cut reveals the profile of the shoe molding on the cut face. You will see a thin curved line where the front face meets the mitered cut — this line is your coping guide.
Using a coping saw, cut along the profile line, removing the wood behind it. Angle the coping saw slightly backward (back-cutting) so that only the very front edge of the coped cut makes contact with the adjoining piece. This ensures a tight fit on the visible face even if the cut is not perfectly smooth behind it.
Hold the coped piece against the first installed piece. The coped end should nest tightly against the face of the first piece. Use a round file, utility knife, or sandpaper to fine-tune the coped edge if there are any high spots preventing a tight fit.
Once the fit is good, nail the coped piece into position. The coped end does not need a nail right at the corner — the pressure of the piece sitting against the adjoining molding holds it tight.
For more on outside corner techniques and scarf joints, see our corner techniques guide.