Does anyone build their own wire cages? I have the wire part down and can build a cage using "J" clips, but I am wondering how you make the aluminum trays that slide underneath. Where do you get the aluminum sheeting? And how do you bend it along a straight line? The only think I can think of is aluminum flashing that comes in rolls from Home Depot. I am wanting to build some stackable cages like this, but need to figure out how to make the trays.