General term for a small device or part that holds two things together, such as on a bag, box, or piece of clothing.
The fastener on my bag broke.
The clasp on this necklace is so small that it's hard to put on.
Standard spelling using 留める (to fasten).
Variant using 止める (to stop); less common but still seen.
Compound of 留め (tome, 'fastening', from verb 留める) and 具 (gu, 'tool, implement').