Like most wood shops that have an open area under the workbench, it soon accumulates all of the left over and scrap wood underneath. When I dug all of mine out to clean the floor, I decided to come up with a better way. I thought about more shelves, but that still leaves room on the floor. Then I thought drawers, big drawers, but the size and strength of the rails would be daunting and expensive. I kept the drawer idea somewhat, but moved the "rails" to the floor in the form of swivel casters. This has the added benefit of being completely unattached, and moveable anywhere.
I first added guide rails to the legs of my workbench, flush with the sides of the legs. They look like shelf supports, but are only meant to guide the drawers since I used all swivel casters. With all swivel casters the drawers will self align once you get it started.
In the case of my shop, each of the spaces between the legs was a little different so each drawer assembly measured accordingly. I left 1/4" clearance on each side, but made all of the drawers the same depth and height. I left several inches between the top of the drawer and the shelf above it so I could drop pieces in without pulling the drawer out.
Next I considered how strong the drawer needed to be and what construction method to use. I decided that 1/2" 3 ply(cheap) plywood, and gluing and nailing all seams was the simplest, and sufficiently rugged for the purpose. I used 1" 18ga nails with an air nailgun.
I added a 4" piece of ply under each set of casters, both for added strength, and so I could use decent size screws for the casters without going through the bottom. Since the material was all 1/2 ply, I could only nail the 4" pieces on the short ends, so those were glued to the drawer bottom also.
A pair of drawer pulls fastened with 1/2" screws completed the drawer.
Hopefully this will keep the scrap material a little more organized, and I have enough drawers to separate plywood, 2", 1", and fireplace kindling into different bins. I even used some of my "scrap" for this project!