The gauge consists of a long beam with two sliding stops. It works using a sliding dovetail joint. The “tails” on the stops slide along the slot in the dovetailed beam. Each stop holds a 1⁄2“-dia. dowel pin to support the metal ruler when it’s flexed. To keep the stops in position, the pins are installed in the upper corners of each stop. As the ruler bends, the ends of the ruler push against the pins, wedging the stops in the groove.