A kit car is an automobile that is available in kit form, i.e. you buy a set of parts that you have to assemble yourself. Usually many major mechanical parts such as the engine an transmission are taken from one or more donor vehicles. Kits vary in completeness from as little as a book of plans to a complete set of all the components required. The definition of a kit car is usually taken to mean that a number of kits are produced by a manufacturer for sale to the public. A car built at home as a one-off to the designs of its builder is termed a Special.