Denver boot

A Denver boot is an Earth law enforcement tool in nearly any continuity.

Used primarily by police and towing companies, a Denver boot is a clamp placed on a parked vehicle's wheel to prevent it from being driven away. Typically, it is used in retaliation for repeated illegal or otherwise unauthorized parking, in anticipation of receiving delinquent payments of parking fees. It is also used in a less formal fashion by certain vigilante crimefighters. Understandably, such a device can be a significant punishment to an alien species that disguises itself as native land vehicles.