Hydraulic jacks come in two basic types—bottle jacks and floor jacks. In a nutshell, hydraulic jacks use pump plungers to move oil through two cylinders. When the plunger is first drawn back with a lift of the handle, it opens the suction valve ball within and draws oil into the pump chamber. As the plunger is pushed forward with a downward press of the handle, the oil moves through an external discharge check valve into the cylinder chamber, and the suction valve closes, which results in pressure building within the cylinder and pushing the jack up. Bottle jacks take up less room to store and use, so excel when jacking up an object in small places. They typically lift smaller loads, up to about 6 tons. Floor jacks are bulkier, harder to store and require plenty of room around whatever object you need to lift. But they are safe and easy to use, and large ones can lift several tons.