The hollow chamber section (4) of the body has at least one flat longitudinal face (5). It also has a flat face (15) of a closed section (8) is fastened to it. This second section (8) has a step-form shoulder (24), the lower end (13) of which lies upon the end face (14) of the hollow chamber section and is connected to it. The connection between the hollow chamber section (4), the open section (6) and the closed section (8) is by adhesive or by form locking or force locking.
