buckle

A buckle is a clasp used to fasten two loose ends of a strap or belt and to adjust its length. Although traditionally made of metal, buckles can also be plastic or leather-wrapped and decorative. They are found on clothing, footwear, bags, and a wide range of equipment, including safety gear and harnesses.

Most buckles share common components: the frame, which forms the opening through which the strap passes; the prong or tongue, a pivoting pin that fits into holes or notches in the strap; the bar, the cross-piece the tongue pivots on; and the chape or end fitting that attaches the strap to the buckle assembly. The strap is looped through the frame, and the prong secures the strap at the desired length by entering a hole or slot.

Common types include frame-and-prong buckles, which are standard for belts and watch straps; side-release buckles, which use a two-part male-female mechanism and are common on backpacks and outdoor gear; and various quick-release or magnetic buckles used for convenience on bags and some apparel. Decorative buckles exist for fashion, while specialized buckles are used in watch bands, shoes, and equipment.

Materials and finishes vary widely. Metal buckles are typically made from steel, brass, zinc alloy, or aluminum; plastic or polymer buckles are lighter and often cheaper. Straps can be leather, fabric, or synthetic materials, and finishes range from polished to brushed or plated for corrosion resistance.

Etymologically, the word derives from the Old French boucle meaning ring or loop. Buckles have ancient origins and have evolved into a ubiquitous, functional fastening in modern apparel and gear.