The middle side and both frame sides are separately produced components. At its end the middle side has a bracket (5) riveted to a rod on the frame side. The rivet (11) acts as a carrier for a catch (12). The bracket has a punched hole (6) at its cross-sectional weak point. Frame sides (7) running parallel to each other have a U- or C-shaped cross-sectional profile (8) with a channel and flanges curved on the edge. They are also linked and aligned to each other by a middle side (1).
