An energy absorber includes a base sheet and a plurality of crush lobes extending from the base sheet. The processing may include heat treating andor shaping. A rocking mechanism is associated with the wheel. There is also provided at least one positioning unit arranged on the guide rail, which includes a trunnion insertable form-fittingly into the shaped opening in the support plate to fix a position of the positioning unit relative to the support plate, and a locking element to lock in place an electronic plug-in unit fully inserted into the guide rail.