Abstract: Driving element (1) comprising a thin part (2) provided with a zone, ductile in the direction of its thickness in such a way as to occupy at least two positions, in at least one of which said zone is arc-shaped, at least one tab (3, 4) fixed at one end to a face of said ductile zone and extending towards the central part of the zone in such a way that, when the zone is molded, the free end (8, 9) of said tab moves away from or towards the face (5) of said thin part, the resulting amplitude of the movement of the free end of the tab being greater than the amplitude of ductility of the thin piece.