A bulldozer or dozer is a large motorized machine that travels on tracks and is equipped with a metal blade to the front for pushing material: soil, sand, snow, rubble, or rock during construction or conversion work. Bulldozers are also called crawlers. When needed, a hook-like device (termed a ripper) can be mounted on the rear to loosen dense materials. Bulldozers can be found on a wide range of sites, mines and quarries, military bases, heavy industry factories, engineering projects, and farms. The word "bulldozer" refers to only a tractor fitted with a dozer blade. The word is sometimes used inaccurately for other earth moving equipment such as front loaders.