• 12 parts
  • Checked September 2026

Parts of a Trailer Jack

An A-frame tongue jack cut open to show its screw, then a swivel jack with a wheel.

Parts of a Trailer Jack

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12
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Write the name of each numbered part.Answer key

  1. Handle (crank)
  2. Outer tube
  3. Screw
  4. Inner tube
  5. Mounting plate
  6. Drop leg
  7. Foot plate
  8. Gears
  9. Swivel plate
  10. Lock pin
  11. Snap ring
  12. Wheel (caster)

Drawn for this site on 2026-09-30 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the hitch the jack lifts the tongue onto

All 12 parts on the diagram

Show the list

A-frame jack 7

  1. Handle (crank) Turning it turns the screw. The screw moves the inner tube out of the outer tube or back in.
  2. Outer tube On an A-frame jack, goes up through the trailer's A-frame tongue. It passes through the hole there. It is drawn with a window cut in it.
  3. Screw The handle turns it. It stays where it is left when you stop turning, which is why a screw jack holds its load.
  4. Inner tube The screw drives it down to lift the tongue. The screw draws it back up for towing.
  5. Mounting plate Its bolt holes line up with holes in the tongue. On a swivel jack the mounting plate is bolted or welded to the side of the tongue.
  6. Drop leg Drops down and is pinned at a hole at the height needed. It is never moved while the jack is carrying the trailer.
  7. Foot plate The jack stands on it, on hard, level ground. Some jacks have a wheel in its place.

Swivel jack 5

  1. Gears Sit between the handle and the screw. A jack with its handle on the side has them. Some jacks have a high gear and a low gear.
  2. Swivel plate The jack turns on it. Upright to hold the trailer, then swung level along the tongue for towing. Its holes take the lock pin.
  3. Lock pin Pull it and the jack can turn. It snaps back into a hole to lock the jack upright or level.
  4. Snap ring Sits in a groove and holds the jack on its mounting plate. It is taken off with snap ring pliers.
  5. Wheel (caster) The front of an unhitched trailer can be moved by hand. That is with the jack wound down, on hard, level ground.

How this list was compiled: Part names checked on 2026-09-30; a name is kept only when two independent makers' instructions use it. (1) Harbor Freight Tools, 2000 lb. drop leg A-frame trailer jack, owner's manual, https://archive.org/details/manualzilla-id-7037568 (crank, outer tube, inner tube, jack screw, mounting plate, lock pin, foot plate); 3500 lb. drop leg trailer jack, https://archive.org/details/manualzilla-id-7037414 (drop leg, lock pin, inner and outer tube, handle); and swing-back trailer jack, https://archive.org/details/manualzilla-id-7037747 (gears, swivel plate, mounting plate, swivel handle pin, wheel, crank). (2) Grizzly Industrial, Model H6162 trailer screw jack, instruction sheet, https://archive.org/details/manualsbase-id-12966 (mounting plate, handle, foot, lock pin that snaps back, external retaining ring taken off with snap ring pliers). (3) Cequent Trailer Products, square jack instructions bound into a trailer owner's manual, https://archive.org/details/manualzilla-id-5956916 (inner tube, drop leg, drop leg pin, footplate, caster wheel, handle, high and low gear), and a bolt-on swivel jack user manual with the same wording, https://archive.org/details/manualzilla-id-6349010 (inner and outer tube assembly, locking pin, swivel plate, snap ring, mounting brackets, handle, screw stem, foot plate); the two count as one source. (4) Wikipedia, text only: Trailer (vehicle), section Jacks (A-frame, swivel and drop-leg jacks), and Jackscrew (a screw jack stays where it is left). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's jack, nothing traced. Licence: own work

How it works

A trailer jack is a screw jack fixed to the trailer's tongue: turn the handle and a tube winds down to lift the tongue off the hitch ball. Two kinds are drawn.

Read the full guide

One screw, two ways to mount it

The A-frame jack goes up through a hole in the tongue and is bolted there by its mounting plate. Its outer tube is drawn with a window, so you can see the screw that the handle turns. The swivel jack is bolted to the side of the tongue. Pull its lock pin and it swings level for towing, as the dashed outline shows.

  • Wind the jack all the way up before towing; a swivel jack is also swung level and locked.
  • This page names the parts; it gives no load ratings.

Questions and answers

What are the parts of a trailer jack?

A handle turns a screw inside an outer tube, and the screw moves an inner tube down or up. A mounting plate fixes the jack to the tongue. At the bottom is a foot plate or a wheel, and some jacks have a drop leg.

What are the types of trailer jacks?

The most common are A-frame jacks, swivel jacks and drop-leg jacks. An A-frame jack stands in the A-frame of the tongue, a swivel jack swings up out of the way, and a drop-leg jack has a leg that is pinned at the height needed.

What is a drop leg on a trailer jack?

A leg with a row of holes that slides out of the bottom of the jack and is held by a pin at the height needed. It is set before the jack takes the trailer's weight, never while it is under load.

How does a swivel trailer jack lock?

A spring-loaded lock pin sits in a hole of the swivel plate. Pull the pin, turn the jack about a quarter turn, and the pin snaps into the next hole.

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