A miter saw or mitre saw is a saw used to make accurate crosscuts and miters in a workpiece by positioning a mounted blade onto a board. A miter saw in its earliest form was composed of a back saw in a miter box, but in modern implementation consists of a powered circular saw that can be positioned at a variety of angles and lowered onto a board positioned against a backstop called the fence. Miter saws are primarily used for cutting wood trim and molding, but also can be used to cut metal, masonry, and plastics, provided the appropriate type of blade is used for the material being cut.