This was my first thought as well, the theory is also mentioned in the article (the small round mushroom-shaped knobs were possibly used to hold the tent cover

This was my first thought as well, the theory is also mentioned in the article (the small round mushroom-shaped knobs were possibly used to hold the tent cover in place). I think I have seen similar standardized joints in modern constructions. E: here is a modern day version, just google for "MERO system": https://www.mero.de/index.php/en/construction-systems/nodes/kk-ball-node-system-en https://www.mero.de/index.php/en/construction-systems/nodes/...