The Dzus fastener is a particular bit of metal that should be familiar to anyone who works with vehicles which have a thin metal skin (or thin metal paneling of any sort). It is used to hold two flat panels together, one atop the other, and is generally used where panels overlap in order to bond multiple panels together horizontally. It is noteworthy for being easy to fasten or unfasten while still resisting loosening from anything other than a positive torque applied to the screw component of the fastener.
It's hard to describe, as it's a relatively complex object, but it generally consists of a central screw, a flat metal frame or grommet through which the screw passes, and a spring wire that sits below the frame and whose central bar connects to the screw. At the spring end, the screw has a curved slot cut in it to engage the spring wire, and it is designed such that slotting the screw over the spring and then turning the screw a quarter-turn to the right will draw the spring wire 'up' the arc and into a locking channel. At this point, the spring is compressed up against the bottom of the grommet, and no vibration or other disturbance will cause the screw to loosen due to the spring exerting tension against the screw. The only way to unfasten the device is to exert positive torque on the screw to overcome the spring resistance and to maintain that torque until the screw has rotated enough to 'lift' the spring bar out of the locking channel and into the curved slot. When the fastener is closed, the spring and the grommet or frame press the two flat surfaces of the panels to be held between them, sometimes with small lugs or dimples which fit into the holes depressions in the panels to prevent them from sliding. Sometimes the fastener is permanently mounted to one panel or the other to prevent its loss and increase its grip.
This makes it ideal for applications where it must often be removed with minimal tools but must work to keep panels secured with high reliability. As a result they were heavily used on aircraft and race cars for coverings which might need to be removed for service, such as panels covering areas where control systems were hidden. They could be opened or locked with a coin of the appropriate minimum size, rather than requiring a specific tool, and would maintain their grip even under the stress and vibration of high-powered vehicle use. They were also known as "quarter-turn fasteners."
The name (pronounced zoose) is that of the inventor of the device, a gentleman named Volodymyr Dzus (William Dzus after his immigration to the United States). He was born in 1895 in Ukraine, and invented and patented the fastener in the U.S.