A nut (6) is inserted into a screw attachment (1), said nut accommodating the head of a fastening element. The nut (6) is made of two cheeks (4, 5) which engage into a sleeve-like holder (3) with torsional rigidity. The cheeks can be moved in axial direction in relation to the holder (3). In one of the end positions, the cheeks (4, 5) can be pressed apart for insertion of the head of a fastening element. By exerting an axial force in the direction of the arrow (23), the cheeks (4, 5) are pressed into the holder (3), whereby the cheeks are forced against each other in a radial direction as a result of their sharp corner contact surfaces (12, 13), so that the inserted head of a fastening element is firmly retained. |