It's a box. It has a lid. It has a hinge. It has a clip to snap shut. You put things in it. Customise it to hold different-sized things, and put a label on the lid so you know what's in it without opening it. Simples!

Want a variation? Either customise yourself (it's easy!) or ask in the comments with the dimensions of the thing you want to store and the label you want on the lid, and I will see what I can do.

Note that the model requires the excellent BOSL2 library (so won't currently work with the online Customizer, which doesn't support this).

The all-in-one (base+lid together) STLs are oriented on the assumption that you are printing in PLA, which has weak layer adhesion - the weak parts are the hinges and clip and they will be liable to breaking in any other orientation. However, this orientation needs a lot of support. I've also included STLs for the bases and lids separately if you want to try another orientation.