Allen wrench holder
I needed a holder to keep my esoteric set of metric Allen wrenches together. (I also made a Gridfinity module to hold this with my pocket knife.) I made it to hold 2mm, 2.5mm, 3mm, 4mm, 5mm, and 6mm wrenches.
Since I’m a sucker for multipurpose tools, I sized the short edge of the holder to 10x20mm and debossed the sizes for reference.