Guitar Strap Lock Round Head Black/Guitar Bass Security Straplocks Strap Retainer, Schaller-style, Guitar Replacements (Pack of 4) An inadvertent loosening of the strap is impossible. So your instrument is always in the best of hands High quality, safe, skidproof, round head straplock Elaborately designed for all kinds of guitars Insert the straplock into the fastening nut Make sure the pin is tightened, then lock the strap to the straplock button