(#10) It fits between the Engine guard/skid plate side and the fuel tank. It's "T" shaped to slide into a slot in the fuel tank and hold the Engine guard/Skid plate in place.
The diagram doesn't really show it, and my dealership wasn't able to find them, but there are supposed to be supporting stiff wire parts keeping these in place. They are fairly critical, as both tank and engine guard damage can occur without them. I ended up fashioning some out of old yard sign wire.