The two vertical bits are to keep the lower wheeled assemble in line.
Without the two vertical bits the lower piece would travel out from under the top piece, with a horrible thud.
This keeps everything aligned.

I will post some pictures with the lifter spread out, but it really only needs to lift the mill a 1/4" at best, just so that there is ground clearance.
The lifters are Honda car jacks, they easily lift the mill.

The link to my website shows more pictures.

Ralph