Roller conveyors are made up of a series of axles that are attached to fixed or telescopic frames. To move items down the line, these unpowered (gravity-flow) conveyors use a downward slope or a manual push. Drums, pails, pallets, skids, and bags all have rimmed or irregular bottoms, and the rollers provide a firm platform for moving them. They allow cargoes to roll along a path from one location to another, saving time and effort in jobs including package handling, storage, docking, assembly, and inspection. Loads can be pushed from side to side across the whole width of the conveyors as they roll forward and back. Conveyors with rollers often have a higher weight capacity than those with skate wheels. The size of the items that can be delivered on the conveyor is affected by the roller spacing density. At all times, at least three rollers should sustain the smallest item on the conveyor.