Great ideas. The trays are super sturdy. I found two tossed in the weeds behind a long-closed convenience store.
I've tried them for sifting compost- the holes are really big so it's a coarse sift at best. A hardware cloth liner would make it a better sifter.
I put them on top of leaf piles to stop them blowing away.
You could zip-tie 6-8 together to make a bin for fall leaves or temporary fence for small area? They're about two feet square, I think?
