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Captive fasteners come are pieces of hardware that are shaped like nuts and typically are mounted within a hollow tube or channel. The fasteners allow a bolt or screw to be tightened into the fastener, joining two parts of an assembly. Captive fasteners are routinely used in difficult-to-reach locations where it would be impossible to place a wrench on the faster. Some fasteners are welded inside of the channel or tubing, and other designs pinch the fastener inside the part, like a rivet.
These fasteners come in an assortment of designs, and a common link between all fasteners is a serrated edge that causes the nut to dig into the material in which it is housed. Some fasteners that are used in wood products have staple-like teeth protruding from the top that sink into the wood and prevent the nut from turning when tightened. Captive fasteners used in metal have sharp serrated edges machined into the surface of the nut that bite into the metal to which they are attached.
Captive fasteners are used in many common household items. The bolts that hold most refrigerator doors on use captive fasteners. Most home entertainment centers are fastened together with the help of captive fasteners. Automobile trunks and hoods as well as most doors are held on using these special fasteners.
Some of these fasteners come in the form of hollow plastic inserts, which are embedded into a wooden product. They serve as a location into which screws can be driven to hold a panel or even a picture in place. Some automobile trims also utilize the plastic inserts and mount the trim pieces in place by running screws through the trim and into the plastic receptor.
Before the advent of the captive fastener, an item required an access hole to tighten parts in place. This created structural weaknesses in many products, which in turn required reinforcing parts to be added to the design. This raised the cost of production, which was passed along to the consumer. The use of captive fasteners allows manufacturers to design products that are easy to assemble, that cost less to manufacture and are sturdy and stable.
The automobile aftermarket has promoted the use of captive fastening devices in the form of Dzus fasteners, or quarter-turn fasteners. This type of fastener utilizes a spring clip onto which a male fastener grabs and locks tight. These fasteners are used to secure hoods, doors and other interior and exterior body panels.