These 3 shelves I purchased are worthless, keep falling apart when I try and assemble, 2 of the 3 boxes had missing parts. I'm following the instructions but they don't like to stay together, I purchased these to hold heavy street signs made of steel for my new business, the bottom shelves should be OK, it's the top 2 I'm worried about, can't get them to stay together safely. Would never purchase these again! Should have looked a the reviews first, which I usually do but didn't for this purchase, lesson learned!