They attach via bolts to the holes in your frame and give you loops for attaching whatever you want.
Put carabiners or s-hooks in there and attach solar lights, or hang a bag or a kitchen kit, secure long lumber up and out of the way when you’re using your truck like a truck…very versatile and adjustable mod for the GFC.
You could also thread gear ties through the loops and use as impromptu drying line, use for hanging shoes, etc. @jondub can make them to order for length so if you wanted to string them along the top or bottom as a line for storage you can do so.
They’re $30 for one or $50 for two. As a (mostly former) climber I have a lot of experience clipping things into a daisy chain so they made a lot of sense for me.