If you're trying to lift something heavy, a jack can be incredibly useful, if not necessary, but do you need a screw jack or ...

Only hydraulic jacks need bleeding, because only hydraulic jacks have oil. It's easy to do, if long and boring, and you usually don't need any tools at all.

Hydraulic jacks operate on the principle of Pascal's law to multiply force. Essentially, pressure is created when a hydraulic jack's lever is pumped, applying force on the fluid inside a chamber.