Measure the wood molding to size and mark the measurements on the back of the molding with a pencil.
Read the directions that are included with your miter box. Each miter box is a little different. Some offer a larger selection of angles while others only offer 90 degree and 45 degree angles.
Set the wood molding into the miter box. The flat edge of the molding should be set against the bottom of the miter box.
Use a hand saw to cut along the appropriate angle in the miter box.
Measure the wood molding to correct size. Mark the measurements on the back of the molding with a pencil.
Decide what angle the wood molding should be cut at. Set the angle on the miter saw to match the angle for your wood. If you have questions about setting your miter saw to the correct angle, refer to the directions included with the miter saw.
Place the wood molding in place on the miter saw. The flat edge of the molding should sit flat against the table of the saw. Once the molding and saw are both in position, make the miter cut.