I'm glad others had the good answer to this, because I didn't know for sure. I just remember reading a few threads about this back in `03 or `04. But I bet those tow hooks would be great for attaching a rappel rope and dropping down some sink holes.
Be safe and tie the end off to your axle. That's how we rappelled down parking garage stairwells in college. Of course, you can use the tow hook as your apex if you're going to pull up over the hole, assuming it's safe to do so.