A wheel clamp, also known as wheel boot, parking boot, or Denver boot, is a device that is designed to prevent motor vehicles from being moved. In its most common form, it consists of a clamp that surrounds a vehicle wheel, designed to prevent removal of both itself and the wheel. In the United States, the device became known as a "Denver boot" after the city of Denver, Colorado, which was the first place in the country to employ them, mostly to force the payment of outstanding parking tickets. While primarily associated with law enforcement and parking violations, a variety of wheel clamps are now available to consumers as theft deterrent devices for personal use as an alternative to the steering-wheel lock. Functions Wheel clamps have five main functions: To punish unauthorised or illegal parking, in lieu of towing the offending vehicle; in these cases, police or property owners who place the clamp may charge a high "release fee" to remove it To enforce unpaid fines previously applied to the vehicle; a certain number of nonpayments or time elapsed from the issuance of the most recent fine results in clamping upon the next violation To prevent driving by a suspended driver or moving of a disabled vehicle To preclude escape of a prosecuted person For security purposes, such as preventing a car, trailer, or caravan from being driven or towed away by a thief History As the automobile was introduced and became popular, cars also became a target for thieves and for a new concept that became known as joyriding. A variety of after-market security devices were introduced. An early invention were locking wheel clamps or chocks that owners could shackle onto one of the car's road wheels as a hobble, making it impossible to roll the vehicle unless the entire wheel was removed. Between 1914 and 1925 there were at least 25 patents related to wheel locks that attached on the tire and spoke wheel. These devices were available in many sizes from a number of manufacturers (including several patented by Miller-Chapman), and became popular during the early 1920s. A version of the modern wheel clamp, originally known as the auto immobiliser, was invented in 1944 and patented in 1958 by Frank Marugg. Marugg was a pattern maker, a violinist with the Denver Symphony Orchestra, and a friend of many Denver politicians and police department officials. The police department