Answer:
I am bought by the yard but worn by the foot
You use me between your head and your toes the more I work the thinner I grow.
What is easy to get into, but hard to get out of?
I can be driven but have no wheels. I can be sliced but still remains whole
I can run but not walk. Wherever I go thought follows close behind.
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.