The hydraulic power unit consists of two fundamental parts, the control unit box, which is the part that supports all the components inside the control unit, and the cover that serves as a cover to protect the components and as access for maintenance. The control unit box is also called a casing or support. In some cases it is metal but it can also be found in plastic. Metal solutions sometimes also serve as oil tanks. The control unit covers, on the other hand, are generally made of plastic, ABS. The hydraulic power units that are housed inside the main frames of the tail lifts have only rubber side cover caps, the frame itself being the container.