A hand pallet jack, also known as a pallet truck

A hand pallet jack, also known as a pallet truck, pallet pump, pump truck, dog, or jigger is a tool used to lift and move pallets. Pallet Jacks are the most basic form of forklift and are intended to move heavy or light pallets within a warehouse.
The jack is steered by a 'tiller' like lever that also acts as the pump handle for raising the jack. A small handle on the tiller releases the hydraulic fluid, causing the forks to lower. The front wheels inside the end of the forks are mounted on levers attached to linkages that go to levers attached to the jack cylinder. As the hydraulic jack at the 'tiller' end is raised, the links force the wheels down, raising the forks vertically above the front wheels, raising the load upward until it clears the floor. The pallet is only lifted enough to clear the floor for subsequent travel. Oftentimes, pallet jacks are used to move and organize pallets inside a trailer, especially when there is no forklift truck access or availability.