Parts of a Floor Jack – Saddle, Lifting Arm, Ram and Pump

All 13 parts on the diagram

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The floor jack 13

Saddle The cup that meets the load.
Lifting arm The ram pushes its short end, and the long end rises.
Handle Pumping it up and down raises the jack.
Front wheel Two wheels on a fixed axle at the front.
Rear caster A small wheel that swivels, so the jack can be steered.
Frame The steel side plates that hold all the other parts.
Handle socket The handle fits into it. It bears on the pump piston.
Release valve Opening it lets the oil back, and the saddle comes down.
Oil reservoir It holds the hydraulic oil that the pump moves.
Ram Oil pressure pushes it out against the lifting arm.
Pump piston Each stroke of the handle drives it to move oil.
Oil fill plug A plug on the reservoir. Oil is added through its hole.
Return spring It pulls the lifting arm back down.

How this list was compiled: Every name checked on 2026-10-01 and kept only where two unrelated makers' owner's manuals use it of a hydraulic floor (trolley) jack, read as page text on archive.org. (1) https://archive.org/details/manualzilla-id-6932035 : parts key (handle, wheel, caster, release valve, saddle, oil fill plug, carrying handle, hydraulic ram, lifting arm, frame), handle socket, return spring, and how it works: the power unit consists of plunger, plunger cavity, hydraulic oil reservoir, cylinder and ram. (2) https://archive.org/details/manualzilla-id-6932139 : parts list (hydraulic unit, caster wheel, lift arm, side member, front wheel, saddle, cover plate, handle base), handle socket, release valve, oil fill plug, ram, pump piston, return spring for the lifting arm. (3) https://archive.org/details/manualzilla-id-7290233 : saddle, handle socket, release valve, caster wheels, lift arm linkages. (4) https://archive.org/details/manualzilla-id-6404235 : parts list (release valve, pump piston, oil reservoir, saddle, lifting arm, link rod, front wheel, castor, frame, handle sleeve, handle). (5) Wikipedia, Jack (device), text only, https://en.wikipedia.org/wiki/Jack_(device) : in a floor jack a horizontal piston pushes the short end of a bellcrank and the long arm lifts the pad; a pump plunger draws oil from the reservoir and pushes it into the cylinder; floor jacks have casters and wheels. Licence: own work

The drawing: Own drawing from plain geometry; nothing traced. Licence: own work

How it works

A floor jack, also called a trolley jack, is the low wheeled jack of a repair shop. The drawing shows one from the side with the near side plate left off, so the hydraulic parts are in view.

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The parts you see

The frame rolls on two front wheels and two rear casters that swivel. The long handle stands in the handle socket. At the other end the lifting arm carries the saddle, the cup that meets the load.

The parts that lift

Each stroke of the handle works the pump piston, which moves oil from the reservoir to the ram. The ram pushes the short end of the lifting arm, so the long end rises. Opening the release valve lets the oil back, and the return spring pulls the arm down.

The quiz takes lift arm for lifting arm, plunger for pump piston and castor for caster.
Makers call the reservoir, pump and ram together the power unit or hydraulic unit.

Questions and answers

What is the saddle on a floor jack?

The saddle is the round cup at the end of the lifting arm. It is the part that touches the load, and on many jacks it can turn.

How does a floor jack lift?

Pumping the handle drives a small pump piston. It pushes oil from the reservoir into a cylinder, where the oil forces out the ram. The ram pushes the short end of the lifting arm and the saddle rises.

What does the release valve do?

It holds the oil in the cylinder while the jack is up. Turning it open lets the oil flow back to the reservoir, so the ram goes in and the saddle comes down.

Why does a floor jack have casters at the rear?

The rear wheels swivel so the jack can be steered into place. The wheels also let the jack roll a little as the arm rises, because the saddle moves along an arc.