Answer:
You can do this with your friends. You can do this with your nose. But don't do it with your friend's nose!
It comes only before, it comes only after. Rises only in darkness, but rises only in light. It is always the same, but is yet always different.
What always comes into the house through the keyhole?
What comes down but never back goes up?
A tower at the root of all confusion.
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.