Stackable trays that take an embedded 30mm x 2mm neodymium magnet. I designed this because I wanted a paperclip tray but didn't want the paperclips to fall out all over if I bumped it.

I designed this around a couple of magnets I happened to have laying around and they work quite well. The magnet cover is meant to be glued in using some CA glue after the magnet is placed inside the cavity.

If you are doing multiple that you want to stack, pay attention to your magnetic pole direction so that they attract instead of oppose each other when you stack the trays on top of each other.