Squares are a fundamental tool for any craftsman. They are used when cutting lumber, setting dowels, laying tile, building stairs...and any number of other jobs. Basic options like steel squares, framing squares and carpentry squares are used to determine simple 90-degree angles. Combination squares feature an adjustable/replaceable head and can measure both 90-degree and 45-degree angles. Rafter angle squares (also known as speed squares) can determine any angle between 0 and 90 degrees.