Strong yet lightweight plastic construction with embossed imperial graduations and lipped edge for secure locating. Calculates rafter angles and can be used as a protractor or as a rafter square. Can also be used as a 90° and 45° mitre square. Strong yet lightweight plastic construction with embossed imperial graduations and lipped edge for secure locating. Calculates rafter angles and can be used as a protractor or as a rafter square. Can also be used as a 90° and 45° mitre square.