When installing house trim you want to get the joints as tight as possible. Some finish carpenters use 45 degree joints but the best way to get a really tight joint is to cope one of the joining pieces. Coping is cutting along one piece of the trim so that it fits perfectly against the shape of another piece. Coping trim is relative easy and any DIY homeowner can master the technique with a little practice.

When installing trim molding in an older home where the walls are not square, it is nearly impossible to get a tight fit unless the joints are coped. Getting a close fitted joint by beveling the trim at 45 degree angles where the inside corners meet is nearly impossible. Even for an experienced finished carpenter this task can be difficult.

Although coping crown molding can be a little more difficult than coping inside corners of baseboard molding, the basic principles are the same. Here are the basic steps for coping molding to have a tight finished joint.

Assuming that the room is a rectangle, the first piece of molding is installed at its full length against the wall, corner to corner. The next piece has the joining piece coped on one end and fitted onto the first piece. Repeat this procedure for the third piece. The forth piece is coped on both ends to fit tightly to the first piece and the third piece you installed.

1. Step one is to buy a coping saw. There is no need to buy an

expensive one. The coping saw's thin blade allows you to saw curves and cut into tight corners. A basic coping saw is available at nearly any hardware store or home improvement supply center. The coping saw blade has twenty teeth per inch and wood well for most all copes. Some finished carpenters prefer to cut copes using a jigsaw with a fine tooth blade.

2. Establish the cutting line by cutting the trim at a 45-degree bevel, Pic1.

3. Clamp the molding onto a sawhorse or hold it in place with your knee while you cut the cope. Don't force the blade while cutting. If the blade starts to leave the cutting line, back up a little and restart the cut.

4. Cut along the paint line of the 45 degree angle

Pic 2.

5. Test-fit the cope on a matching piece of trim. Some copes fit perfectly on the first try and others may require a little filing or sanding before you get a good fit, Pic 3.

Coping 1

Coping 2

Coping 3

See related DIY articles.