This one’s known by lots of different names, including a Jumping Jack, Rammer-Tamper, or just Rammer.  It’s function is straightforward - jump up and down with as much force as possible, as often as possible, to compact the materials beneath it.

A rammer is different than a vibratory plate in that instead of violently shaking materials to get them to settle and compact, a rammer simply applies brute force to the material beneath it, like a fist pounding into the dirt or a person jumping up and down.

But make no mistake - unless you weigh 3,000 pounds and are still able to jump, you won’t be able to manually generate the same compaction force as a rammer.  Stick to the power tools - they’ll always do a better job for you.

The reason you’d want to use a rammer over a plate vibrator has to do with the material you’ll be compacting.  Crushed aggregate stone compacts to a higher density and greater uniformity under a plate vibrator, while a material like clay, where each particle is flat and wide like a platelet,  a vibratory compactor will do little to settle out this material because it won’t naturally settle out with vibration.  What’s needed are repeated, compacting blows to the material, like a fist pounding on dough.  This will remove air pockets, water pockets and help align those soil particles.

For poorly compacting soils, the use of a rammer is the preferred way to achieve maximum material density.