This guard is meant to complement Wassi's design found here:
https://www.thingiverse.com/thing:3972149
It will protect the chain from snagging at the corner of the bed frame and relieve stress by supporting the chain from underneath.
You'll just need to remove the extrusion's cap before you push it down over the frame.
The author marked this model as their own original creation. Imported from Thingiverse.