Stackers have forks that slide underneath or into openings on pallets, skids, and containers, and they have a hydraulic pump or hand crank that lifts the loaded forks. Also called pallet stackers, these wheeled vehicles move heavy loads and lift them in order to stack them or place them onto storage racks or other high surfaces in warehouses, manufacturing plants, construction sites, and other industrial settings. Stackers need less maintenance and can maneuver more easily in tight spaces than forklifts, and they don't require certification to operate. Optional stacker accessories can be used to allow the stackers to hold small or irregularly shaped loads.