High quality material: Made of aluminum alloy with anodic oxidation treatment, it is durable and rust-proof. High hardness, anti-rust, non-corrosive, permanent use. Perfect 90 corners: This precise clamping square is designed to be fixed on boxes, frames, etc. to help square it up when gluing. This right angle positioner has two additional slots. True right angles for interior and exterior squares. Ground and folded down for straightness and parallelism. How to use: Place a square in the corner of the two pieces you need to square and secure with a set of pliers. With metric and inch scales. Accurate calibration, easy operation, not easy to damage fragile cutting edges. Available in 12cm, and comes in a set of two. Professional design: designed to attach to boxes, picture frames, shelf cabinets and for outside corners etc. to help square when gluing. Beveled edges, easy to handle and won't damage fragile cutting edges. Wide Application: You'll have exactly what you need to create perfectly square boxes, drawers, cabinets, frames, cabinets furniture, etc. Some carpenters even find it useful to incorporate them into their jigs and fixtures. Satisfaction, high utility, efficiency square.