ลูกกลิ้งลําเลียงอัตโนมัติ takes less effort to move loads than unpowered (gravity-flow) roller conveyors. They convey items at a controlled speed with even spacing and are typically used in warehousing, manufacturing, package handling, and distribution applications. Each conveyor section consists of rollers that are mounted on a series of axles attached to a frame. A motor-driven belt, chain, or shaft turns the rollers, so these conveyors do not require a manual push or slope to move loads down the line. The rollers provide a stable surface for moving loads with rimmed or uneven bottoms, such as drums, pails, pallets, skids, and bags. Loads roll forward along the conveyor, and they can be pushed from side to side across the width of the conveyor. The conveyor's roller spacing density affects the size of the items that can be conveyed on it. The smallest item on the conveyor should be supported by at least three rollers at all times.