A car crusher is an industrial device used to reduce the dimensions of derelict (depreciated) cars prior to transport for recycling.

Car crushers are compactors and can be of two types: "pancake", where a scrap automobile is flattened by a huge descending hydraulically-powered plate, or the baling press type, with which the automobile is compressed from several directions until it resembles a large cube.

Car crushers can be stationary or mobile

http://en.wikipedia.org/wiki/Car_crusher