Answer:
I make billions of dollars selling windows. Who am I?
I am commonly abbreviated to H
I am two-faced but bear only one. I have no legs but travel widely. Men spill much blood over me. Kings leave their imprint on me. I have greatest power when given away yet lust for me keeps me locked away.
My first though water cures no thirst my next alone has soul and when he lives upon my first he then is called my whole.
You use me between your head and your toes the more I work the thinner I grow.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.