Wheel clamp

A wheel clamp, also known as wheel boot, parking boot, or Denver boot, is a device that is designed to prevent 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 in the country to employ them, mostly to force the payment of outstanding parking tickets.

Wheel clamps have five main functions:

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.

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 needed a solution to a growing parking enforcement problem. The city used to tow all ticketed cars to the pound, where they were often vandalised. Those who were ticketed sued the city for the damage and the police had to itemise everything in the cars. Dan Stills, a policeman, thought an immobiliser would avoid the expensive towing problem and approached Marugg with an idea on how to immobilise a vehicle.

The Denver police first used the wheel boot on 5 January 1955 and collected over US$18,000 (US$160,927 in 2017 dollars) in its first month of use. Although the wheel boot was first cast in steel, Marugg soon switched to a lighter aluminum-based alloy. Marugg later sold the device to parking lot owners, hotels and ski resorts, as well as a Jumbo version for farm equipment and larger vehicles. The Smithsonian Institution now has a copy of Marugg's boot on display in Washington, D.C.By 1970 Marugg had sold 2000 boots. Although the patent ran out in 1976 and modern tire rims necessitated a redesign, Marugg's daughter kept up the business until 1986. Clancy Systems International, Inc. later bought the rights to the boot. The boot allowed Denver to maintain one of the largest collection rates for parking fines of any city in the US through its first fifty years.

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