Shelf Support
thingiverse
Book shelves need corner supports. These are the bits that hold the shelf. I tried to use the ones available from local shops, but they break. Here is my design. I used PLA on an Enver 3 V2 and the printed item lasted really long. You would need a 5mm stud that goes into the round pocket. Feel free to use it.
Download Model from thingiverse
With this file you will be able to print Shelf Support 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 Support.