The RST Aluminium Black Rafter Square is a strong-framed, versatile item. Its imperial markings are clear and easy to read. The large base provides extra grip on materials. There is also a pivot point making marking out angles extremely easy. Features: Laser etched markings for easy reading, heavy-duty aluminium construction, handy pivot point, common rafter scale, imperial measurements. Specification: Part Number: RSTRAS12, Size: 12 Inch, Measurement Scale: Imperial.