Abstract: In a one-piece fastener, particularly for jewelry, which consists of two fastening members which are mounted at their one end for pivoting in a common axis of rotation and can be detachably connected at their other ends, one fastening member is constructed in the form of an inherently resilient double hook (2) with hook openings (8, 10) directed oppositely at each side of the tension axis (24) and the other fastening member is constructed in the form of a hinged locking means (1), the double hook being articulated on the hinged locking means (1) by one hook end being able to be frictionally secured in position on the hinged locking means (1) by its other end, through a detent (5) and a counter detent (7). Double hook (2) and hinged locking means (1) are pivotable through 360 degrees, crossing over and passing the detent, for the opening and closing of the fastener and are so constructed that a pivotal movement in one direction opens one hook opening (9) and closes the other (10) and vice versa.