A grader is an engineering vehicle with a large blade used to create a flat surface. Typical models have three axles, with the engine and cab situated above the rear axles at one end of the vehicle and a third axle at the front end of the vehicle, with the blade in between.
In civil engineering, the grader's purpose is to "finish grade" (refine, set precisely) the "rough grading" performed by heavier engineering vehicles such as scrapers and bulldozers.
