The jack can be divided into rack jack, screw jack and hydraulic (oil pressure) jack according to the structural characteristics. In other ways, it can be divided into separate jack, horizontal jack, claw jack, synchronous jack, hydraulic jack, electric jack, etc. The commonly used jacks include screw jack, hydraulic jack, electric jack, etc.

(1) Screw jack. The thread of the screw jack has no self-locking effect and is equipped with a brake. Release the brake, and the weight can be lowered automatically and quickly, reducing the return time, but the structure of this jack is complex. The screw jack can support heavy objects for a long time, and the maximum lifting capacity has reached 100 t, which is widely used. After the horizontal screw is installed on the lower part, the weight can also be moved laterally in a small distance.

(2) Hydraulic jack. It is used as an intermediate medium in the hydraulic transmission system to transfer and convert energy. When used, it also plays the role of lubrication, anti-corrosion, cooling, flushing, etc. among various components in the hydraulic system.

(3) Electric jack. A pressure retaining device is installed inside the jack to prevent overpressure. If overpressure occurs, the jack will not return to a certain position. The special structure can play a double protection role for the jack. After the diving device is installed on the lower jack, the purpose of low height and high stroke can be achieved.