No matter what you’re building with wood, it’s likely to have some corners. This means you’ll need to know how to cut angles into your wood with some precision so your piece will work properly. A miter saw helps with this a great deal, as it tells you the angle at which you’re cutting. It’s your job to figure out the angle you need to cut into the wood. With the use of a protractor, a pencil and a little concentration, it’s easy to cut the proper angles and build attractive and functional pieces.
If you don't know the basics of geometry, learn them. If you’re building a frame, you’re probably dealing with a lot of 90-degree (or right) angles. To fit two pieces into a right angle, you’ll need to cut two 45-degree angles, one on each side. You'll need a protractor, that half-circle shape with the measured lines that represent angles.
Figure out the angle you need from your plans or by examining the piece as you’re building it. If you’re looking at detailed plans, the designer will often include the angle you need to cut. If not, you can use the protractor on the plans to measure the proper angle. If you’re not working with scale plans, fit the two pieces you need to cut together roughly where they belong. Measure the angle this way, but allow for a little bit of error.
Measure twice, cut once. Take your time when you’re measuring the angle at which you want to cut your wood. You can always cut a little more off at the end, but once you’ve cut your wood, you can’t replace it. Check the angle a couple times, and then make a straight pencil mark across the wood when you need to make the cut.
Unscrew the miter saw’s adjustable guard. You’ll see measured angles on your miter saw, just like on your protractor. Line up the arrow on the proper number to know you’re cutting the right angle. Some saws project a laser beam on the wood so you can arrange your pencil marks more accurately.
Fire up the saw and cut along the line you made. Double check the pieces you’ve cut to make sure they go together as you intended, and adjust as necessary.