Zipper is a fastening device which consists of two chains of metal or synthetic material, with a series of teeth clamped along the edge of a strong textile tape. Teeth with spiral or ball and pocket devices are inter-locked by means of slider. Stops are fitted at the top and bottom of the tape to prevent the slider from slipping off. Each tooth has a small protrusion on its upper face and a hollow on its lower face. When the protruded portion of teeth in one chain engages with the recesses (hollow) in the other, the zipper fastens. Opposite movement of slide separates the chains.
