Box clasp (jewellery)

A box clasp is a jewellery fastening with a small housing and a spring tongue that slides inside and engages a catch. It is used on bracelets, bangles and necklaces. The housing may be visibly separate or integrated into the surrounding design, so a box clasp need not have an obvious square outline.

In a common arrangement, pressing the release disengages the tongue so the two parts can separate. Some examples have an additional safety catch, often shaped like a figure eight, at one or both sides. This is a separate safeguard alongside the main fastening mechanism.

When buying used jewellery, gently test both the main clasp and any safety. Look for looseness, distortion, repairs and whether the tongue remains engaged under a light pull. A safety catch does not repair a worn main clasp. Avoid repeatedly bending a weak tongue yourself; a jeweller can assess adjustment or replacement. The type of fastening alone cannot date the piece.

Sources: Erhard Brepohl: Chain and Bracelet Catches 2; Charles Lewton-Brain: Different Types of Knuckle Hinges; Helles Gull og Sølv: dokumentert kasselås på collier.