Abstract: A fastener for jewelry and the like comprises a box-shaped structure made of foil and has, at both ends, two transverse seats which receive fastening elements of a chain or the like to which the fastener is attached. One end is formed by a half-open hook which is closed by a resiliently mounted tongue forming part of the box-shaped structure. The tongue is shaped to increase its stiffness so that the fastener will not become unfastened accidentally despite the fact that the foil is of soft metal such as gold.