The Starrett Prosite® Protractor takes the error-prone calculations out of the process of mitre cuts. Simply set your saw to the angle that you read. Upside down or backwards, the reading is always correct. This easy-to-use tool has two scales. The ' Mitre Cut' arrow & internal scale indicate the exact mitre saw setting for an accurate mitre joint every time. The ' Single Cut' arrow & the outer scale indicate the exact mitre saw setting for fitting a single work piece to an angle. It is ideal for carpenters, plumbers & all building trades that require the measuring & transfer of angles.