This is a 3-inch speed trim square. It is helpful for some applications that benefit from a tool that's much smaller than the more widely available 4-inch square. It is also loosely based on the Swanson 4-inch square. There are also degree measurements on the square. It is made using a 3D printer with PLA plastic. Use it for applications such as welding, woodworking, or carpentry. However, note that very high temperatures can melt the plastic.