High Quality Material: Made of aluminum alloy with anodic oxidation treatment, it is durable and rustproof. High hardness, rustproof, non-corrosive, permanent use. Perfect 90° Corners: This precise clamping square is designed to be clamped on boxes, frames, etc. to help you square during gluing. This right angle positioner has two notches. True right angle for inside and outside squares. Base and folded for straight and parallel. How to Use: Place a square in the corner of the two pieces you need to square and secure with a set of clamps. Metric and inch graduations. Accurate calibration, easy operation, will not easily damage fragile cutting edges. Professional Design: Designed to be attached to boxes, picture frames, shelf cabinets and for outside corners, etc., to help square when gluing. Beveled edges, easy to handle and will not damage fragile cutting edges. Wide Application: You will have exactly what you need to perfectly create boxes, drawers, cabinets, frames, furniture, etc.