Answer:
With head without hair. With mouth without tooth.
We are all around, yet to us you are half blind. Sunlight makes us invisible, and difficult to find
I go around in circles, but always straight ahead. Never complain, no matter where I am led.
I'm tall in the morning and short in the noon. I disappear at night but I will be back soon.
What goes up but never comes down?
You use it between your head and your toes, the more it works the thinner it grows.