The invention relates to a U-shaped clamping piece for attachment to a panel provided with an opening, having two flat legs, connected by a yoke, with a nut part axially movably disposed between the two legs for receiving a bolt, said bolt penetrating the opening and one leg, wherein said nut part is non-rotatably held on the clamping piece by a lateral arm. The nut part is secured by its end in axially resilient manner to the leg facing away from the panel by means of a plurality of straps extending from the end of the nut part to the leg.