buckle

ˈbʌk(ə)l

noun

a flat, typically rectangular frame with a hinged pin, used for joining the ends of a belt or strap.

most rucksacks have quick release buckles

clasp,clip,catch,fastener,fastening,hasp

verb

fasten with a buckle.

he buckled his belt

fasten,do up,hook,strap,tie,secure,clasp,catch,clip