The second guide rail (22) is moved along the first guide rail (20) on the side of the main body (12) by means of roller bodies in a cage. The second guide rail is movable between a pushed-in position and pulled-out end position. A pair of brake elements (100,102) are moved towards each other to reach an end position. One of the brake elements is in the form of an especially conically tapering holder into which moves the other brake element, and subsequently generates an opposing rotation brake operation.
