The Denver Boot or "boot" is a wheel clamp for automobiles. Constructed of metal, the Denver Boot clamps on to a car's tire (usually the front) and makes the car undrivable. This device is mainly employed by cities and towns against people who have amassed too many parking tickets. It consists of two round plates that connect with rods to a hinge. The two plates can be moved closer together(by use of a nut that requires a special wrench) until it is tight against both the hubcap and back of the wheel. The plates are large enough to prevent access to the lug nuts of the tire.
The Denver Boot was invented in 1953 by Frank Marugg I hate his invention, but he seemed to be a talented guy. He was a inventor by trade, but he also was a musician for the Denver Symphony, even making his own violin, and he was a friend to Denver's law enforcement community. They asked Frank for a immobilization device for the parking problems in downtown Denver and the boot is what Frank came up with.
The Marugg family, ran the boot company until the late 1980's, at which time the company was sold to Clancy Systems International Inc which still manufactures the boot. Other companies make the boot, but all use variations of Frank's design.