A Spool Shelf made to use with 20x20 aluminum extrusion.
 

Material Used:

• 20x20 aluminum extrusion
• M4 screws (20 mm to fix the shelf x4)
• M4 screws (10 mm to fix the T-slot x4) - optional
• hammer nut - M4 - 20x20 (fix the aluminiun x4) - optional

Good to use with spool holder - https://www.printables.com/model/503533-spool-holder-for-spool-shelf-t-slot