A place to attach a label (or write directly on it), for spools that are stored vertically. Flat section fits 1.5" x 1" labels.

I was inspired by another model (https://makerworld.com/en/models/1141190), but didn't love how it attached, or that it would prevent the spools from lying flat. 

This model is not quite as strong (you can break the pegs if you try), but I have inserted and removed several dozen times with no issues. Default print profile includes brims, but I have printed several without. So you can likely omit them, but caveat emptor. Basic PLA works great, but other materials would be even stronger.