Steps: 1. Begin with the most difficult cut, the one where the new molding fits against the existing trim. Corners will have to be cut at two angles, and you'll need to adjust the bevel and table cuts on the miter saw.
2. Cut the first angle with the miter saw, but you'll have to use a coping saw to cut away the back of the new trim (figure A). Remember to wear safety glasses when using a power saw.
3. After making the first cut with the miter saw (figure B), highlight the profile of the molding with a pencil and use the coping saw to cut away the back (figure C).
4. Trim up the cut with a utility knife, then file it smooth with a wood rasp (figure D).
5. Once that cut is made and lines up nicely (figure E), the rest should go fairly easily.
6. Set the miter saw to make 45-degree cuts and cut a couple of test strips from scrap molding pieces and test-fit them in a corner (figure F).
7. Drill pilot holes before nailing molding. Attach molding with finishing nails and use a nail set to sink the heads. Cover hail
8. Sink nail heads with nail set and cover up with a putty stick. Cover gaps in molding with paintable caulk.