/!\ STOP HERE, READ THIS:
Edit 20/04/2020: I would suggest you use my recent remix, as it offer more flexibility: https://www.printables.com/model/175051

Most bracket are placed under the shelves but I had this weird tiny space where I couldn't install bracket under the rack… So I designed this simple reversible bracket system for storing filament (see pictures).
Hope it helps !
The author marked this model as their own original creation.