Answer:
Goes over all the hills and hollows, Bites hard, but never swallows.
Never resting, never still. Moving silently from hill to hill. It does not walk, run or trot. All is cool where it is not. What is it?
I am the key that is the hardest to turn
I am black when you buy me, red when you use me. When I turn white, you know it's time to throw me away. What am I?
The person who makes me doesn't need me. The person who buys me doesn't use me. The person who uses me doesn't know it. What am I?
I am your mother's brother's only brother in law. Who am I?