This Ruler Position Block is used with steel straight ruler (not included) for length and width measures, the design was good for marking at both 45°and 90°. It’s suitable for 26-30mm width, approx. 2mm thickness ruler. The ruler is easy to clamp and release via rotating brass screw. The block is made by premium aluminum alloy after excellent oxidation surface treatment, providing wear-resistant, rust-proof and long life. MG45 is east to use and good tool for DIY projects.