A brooch fastener is a device used to secure a brooch or other type of jewelry. It typically consists of two parts: a CLASP, which is a hinged or sliding mechanism that opens and closes, and a PIN, which is a thin metal rod with a sharp point at one end. The CLASP is attached to the back of the brooch, while the PIN is inserted through the fabric or other material that the brooch is being attached to. The PIN is then secured in place by the CLASP, thus providing a secure fastening for the brooch.