Oops, sorry "My friend says to think outside the box on this one" is not part of the teaser. I was just saying that the book my friend got this teaser from says you need to think outside the box to get the answer.
A friend of mine asked me this short teaser and I can't seem to figure it out:
At opposite ends are my mouth and my head
I run for miles without leaving my bed
My friend says to think outside the box on this one.