Answer:
You use me between your head and your toes the more I work the thinner I grow.
I've been around for millions of years, but I am no more than a month old. What am I?
I can be written, I can be spoken, I can be exposed, I can be broken. What am I?
I go around a yard but does not move.
I am in the past never in the future. I don't exist but have existed. I saw what you saw and that is what I will ever see.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.