A Hydraulic Chasis Jack consists of two pistons inside the cylinder that is responsible for lifting the heavyweight. The bigger and smaller cylinder is connected together. The small piston forces the fluid to lift the big piston. The chassis, or frame, forms the basis for the rest of the vehicle. Everything else is built on the chassis. This type of trolley jack has a foot pedal, which gives room for the user to raise the saddle up to the load. Hydraulic Chasis Jack is very useful.