Safety Chain
A short secondary chain bridging a clasp, so the piece is still held if the main clasp opens.
It attaches either side of the clasp and hangs slack, taking no load until something fails.
It is standard on antique bracelets and on any piece heavy enough that losing it would matter.
The figure-eight catch on a box clasp does the same job in a smaller way.
When you are buying
Worth adding retrospectively to any inherited or high-value bracelet. It costs very little and it is the difference between a repair and a loss.
Clasp
The fastening that closes a necklace or bracelet. The most common point of failure and the most overlooked part of a purchase.
Box Clasp
A folded metal tongue that clicks into a box. The traditional fine-jewellery clasp, usually with a safety catch.
Magnetic Clasp
Two magnets that snap together. The easiest clasp to use and the least secure.
Jump Ring
A small metal ring joining two parts of a piece. The commonest failure point after the clasp.