I buy a lot of stuff from AliExpress, and screws and bolts usually come in the same size assortment boxes. Rather than just having them float around in the drawers, or stacking them in precarious piles on my shelfs, I made this stackable shelf for them. 

They are made for assortment boxes sized 129x66x22mm. 

Glue them together with super-glue, and reclaim an orderly parts-shelf!