Wash and thoroughly dry the aluminum can. Place the can on a piece of cardboard and trace around it. Cut the round slightly smaller than the tracing mark so it will fit nicely in the bottom of the can. Place the round cut out in the can. Now, measure the height from the insert to the top of the can. Transfer this measurement to the corrugated cardboard. Cut the cardboard to the desired height. Next, roll the cardboard to fit comfortably in the can, making sure there is slight room for adjustment. It will be best to position the cut side down since it will be compressed from the cutting. You can now slide your files into the corrugations that will keep them separated and safe from knocking against each other.
To easily identify the files, color code them by wrapping pieces of colored tape around the handles, as well as write on pieces of the corresponding tape affixed to the outside of the can.