The RS PRO double square is a precision measuring tool used in various industries. It consists of two components a head and a blade, both of which are made of hardened steel with satin chrome plating. The "double" aspect of the tool means it can be used both as an outside and an inside measurement tool. It's versatile and reliable for tasks requiring high precision and accuracy in maintaining or creating right angles. The precision double square is an essential tool for ensuring the accuracy of various construction, fabrication, and manufacturing projects.