The purpose is to prevent the rotation of the entire aggregate, only the tool shall rotate.
This is normally done by means of a retaining bolt, which is attached on the angular aggregate. This engages in a corresponding depression on the machine, and thus fixes the position of the aggregate.
A torque support is usually used as a driver in order to generate the positioning motion in machines with a C-axis. For this purpose, it can rotate around the working spindle with a servo motor and thus take any position in an angle of 360 ° about the Z-axis.
Several manufacturers offer special forms with multiple retaining bolts or additional interfaces for pneumatics and electronics.