I bought these dividers thinking I would use them as shown in the picture, but these things really grip closet shelves extremely well. Now I store all my books on the top shelf in the closet and like it says holds even heavy books.There is no book it can't support. Very well made. I'll be buying more to store my sons books in his closet once I install a shelf higher up in his closet.
I can't really think of anything wrong with them, except maybe if they were taller and wider to store bath towels.