Planer gauges are used to accurately set shaper and planer tools. Also known as shaper gauges, the main body of the planer gauge is a right triangular metal frame with a groove running along the longest side of the triangle. A solid steel slide travels along that groove. The slide usually has multiple tapped holes in different positions and orientations to accommodate an included extension nib that offers flat, parallel extended reach to position or indirectly measure. The slide has a thinner flat face toward the base of the gauge and it is used to define the minimum measurement. It also has a taller face toward the upper end of the gauge to calculate the maximum measurement from the top of the tall face directly down to the plane of the base.