How the slider rheostat works. How can you include it in the chain?

A slider rheostat consists of a ceramic cylinder on which a steel wire is wound, covered with a thin layer of non-conductive dross to insulate the turns from each other. Above the winding there is a metal rod, along which a slider can move, pressed by the contacts to the winding turns. The rheostat is connected to the circuit with a terminal from the rod on one side and a terminal from the end of the winding on the other side.