In many jackets and similar garments, the opening is closed entirely when the slider is at one of the ends of the tape. The mechanism
allows for partial fastening where only some of the tape is fastened together, but various movements and pressures may move the slider around the tape. In many kinds of luggage, there are two sliders on the tape, mounted in opposite directions; the part of the zipper between them is unfastened. When the sliders are located at opposite ends of the tape, the zipper is fully unfastened; when the two sliders are located next to each other, which can be at any point along the tape, the zipper is fully closed.
Zippers may * increase or decrease the size of an opening to allow or restrict the passage of objects, as in the fly of trousers or in a pocket. * join or separate two ends or sides of a single garment, as in the front of a jacket, dress or skirt. * attach or detach a separable part of the garment to or from another, as in the conversion between trousers and shorts or the connection / disconnection of a hood and a coat. * decorate an item.
These variations are achieved by sewing one end of the zipper together, sewing both ends together, or allowing both ends of the zipper to fall completely apart.
A zipper costs relatively little, but if it fails, the garment may be unusable until the zipper is repaired or replaced—which can be quite difficult and expensive. Problems often lie with the zipper slider; when it becomes worn it does not properly align and join the alternating teeth. If a zipper fails, it can either jam (i.e. get stuck) or partially break off.