A combination square is a versatile precision measuring and marking tool used to check, measure, and transfer accurate angles and dimensions during fabrication, installation, and maintenance work. It consists of a graduated steel rule and an adjustable head that can be locked securely in position for consistent measurements. The tool is commonly used to verify 90-degree and 45-degree angles, measure depth and height, mark straight layout lines, and inspect the squareness of workpieces. Some models include a built-in spirit level and scriber for added functionality. Combination squares are widely used by carpenters, machinists, metal fabricators, welders, engineers, and maintenance technicians in workshops and construction sites. Its durable construction, high accuracy, and ease of adjustment make it an essential tool for precision layout.