shelf leveler
thingiverse
I purchased the "Seville Classics 2-Tier Iron Mesh Adjustable Floating Wall Shelves, 36″ x 14″, Satin Pewter" from Amazon. These mesh shelves are nice, but the manufacturing tolerances are significantly off and the shelves tilt precariously downward. You can find details on how to fix this issue here: https://www.risley.net/rnwp/index.php/2018/04/29/fixing-shelves/. This is a very simple component, designed in FreeCAD. It's a spacer (you'll need four) that slides onto the shelf bracket and adjusts the shelves to a more horizontal position. I've included the FreeCAD files so you can modify them if your shelves aren't off by the same amount as mine.
With this file you will be able to print shelf leveler with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on shelf leveler.