How to Figure Angles for Cutting Wood

Draw a full-scale footprint, using a straightedge, of two boards joined together at angles on a piece of scrap wood. Draw another line intersecting the two boards, perpendicular across the footprint to represent the angle.

Open a bevel square by separating the tongue from the handle. Place the handle of the bevel square on the outside perimeter of the footprint. Align the tongue of the bevel square with the line that represents the angle. Twist the wing nut on the bevel square to lock in the angle.

Place the bevel square on a table saw with the tongue flush alongside the left side of the blade. Place the miter gauge on the table saw. Slide it forward and swivel the fence on the miter gauge flush with the handle. Lock the miter gauge by twisting the handle.

Place the bevel square on a miter saw if you're not comfortable with a table saw or don't have one available. Place the handle of the bevel square flush with the miter saw fence. Loosen the lock on the blade. Swing the blade left or right to flush it with the tongue on the bevel square. Lock the blade in this position.

Cut two test boards using either the table saw with the locked miter gauge or the miter saw with the locked blade.

Place the test boards on the footprint. If the angle is open on the outside perimeter of the footprint, the angle is too steep. Reduce the degree on the miter gauge or miter saw 2 degrees. Trim the boards and test again. Repeat this step if necessary until the angle is tight. If the angle is open on the inside of the footprint, the angle is too shallow. Decrease the degree and repeat this step.