A sine bar and a sine plate are used identically in practice. Using gauge blocks, the sine bar or sine plate is placed at the desired angle, or an angle that matches the workpiece. When placed directly under the upper cylinder, an ABC right triangle prism is formed which then serves as the basis for your measurements. This triangle allows you to apply the sine equation from trigonometry to calculate a range of measurements. This is where sine bars and sine plates get their name. For the now formed triangle, the vertical face ends at the axis of the upper cylinder and goes through the gauge block, the base is horizontal above the surface of the sine bar or sine plate and ends at the axis of the lower cylinder, and the hypotenuse lies parallel to the top surface of the workpiece and ends in each of the two cylinders of the tool. During measurements, the cylinders ensure that the triangle hypotenuse length is consistent during any changes in the angle and are used as contact points during measurement. The most common distances between the centers of each cylinder are 5” and 10” making the necessary calculations more convenient.