noun
General term for a small device or part that holds two things together, such as on a bag, box, or piece of clothing.
バッグの留め具が壊れてしまった。
The fastener on my bag broke.
このネックレスは留め具が小さいので、つけるのが難しい。
The clasp on this necklace is so small that it's hard to put on.
Compound of 留め (tome, 'fastening', from verb 留める) and 具 (gu, 'tool, implement').