This part creats some tension on the metal side panels of the Original Prusa XL, which leads to less resonance on those while printing. Effectively reducing the rattle sounds on thos panels (only). If the part alone is not helping enough in your case, you can try to put some foam adhesive on the tip of it for even more dampening effect.
See installation instruction photo for the installation process. No additional hardware is needed.
Printing advice:
The author marked this model as their own original creation.