I know the answer to this one
He uses these: http://www.safco.org/products.php?pID=240&catID=5
They come 50 per box. Here is part of the PM I received when I asked the same question. Hope this is okay to post, Mike
"I just drilled a 1/4" hole in each bottom corner of each tub, all the way through the lid of the tub below it, and pressed one of these through each hole. Then I took it apart by snapping all the lids off, and used a small pair of snips to clip the little points off the end. Then, a small hook into a stud in the wall, and just a hole through the top tub's lids to use a short piece of string to tie it to the hook in the wall.
The shelf sections are just taped together with clear ducktape, which gives them a wide enough combined base to be completely stable to stand alone."
Hope this helps!
Edit: He also used the 18 gallon containers because they line up just right with the shelving he used