OK, those ain't jacks, they're helper conditioners.
You get a helper who doesn't listen and execute, you have him (or her today) grab a pair of those and follow you around ALL day. NEVER use the aluminum jacks for Conditioning.
On a serious note,, ALL ratcheting post jack manufacturers make 2 varietys and they look alike.
The variety made for lifting and lowering everything ratchets the load DOWN 1 notch per stroke of the handle.
RAILROAD jacks drop the load all the way to the bottom with 1 stroke of the handle.
If you don't understand the difference, grab onto those jacks in the picture and follow me.