Known for outfitting tractors and crawlers, the dozer blade actually came into existence before either machine did. The early dozer blade was pulled by two mules and consisted of a frame outfitted with a blade. The blade was used to fill holes and gullies by pushing and spreading piles of dirt into them.
While many refer to the bulldozer as the tractor and blade combination, the term actually refers to the blade itself. The first manufacturer to fit a blade on a tractor is debatable. Some of the earliest manufacturers to do so include La-Plante Choate Co., and LeTourneau founder, Robert Gilmore LeTourneau.
Dozer blades are available in various types, which include a straight blade, a universal blade, and a straight-universal combination. A straight or S-blade, is short, lacks lateral curving, and is generally used for fine grading of materials. The universal or U-blade is tall and curved, with a large side that is capable of pushing heavier and larger quantities. The S-U combination has features of both, consisting of a shorter blade with a slight curve and small side wings. This type is typically used in mining operations or on some construction sites that require the removal or displacement of large rocks.