The screw jack is a mechanical structure jack. It differs from the hydraulic jack in that it does not contain liquid inside. The interior consists of gears, allowing for lifting both horizontally and vertically. When installing the jack, the bottom support surface of the jack should be solid, and the working area at the top should take into account the local stability of the workpiece. The jack should be placed on a stable, flat, and solid foundation or ground. Usually, wooden or steel plates are placed under the base to increase the bearing area, prevent the screw jack from sinking or tilting, and ensure that its head fully contacts the background object to avoid point contact or line contact. The tonnage specifications range from 3.2 tons to 200 tons. Its color is usually green or red.