The plastic box in the left front is made for (and sold with) 12 x 12 hanging file folders.
Once my projects are almost complete but need letters added, mats made, and the pages assembled, tweaked and put together they go in a manila file folder (much smaller than the 12 x 12 pages but it keeps them together.
Then those files with about 10 layouts to complete go in this hanging file container.
The wagon is always ready for a crop and supplies are almost all duplicates - extra trimmer, scissors, scrap ruler, ATG and other things so I don't have to get things together to go to crops. Its already together.