Answer:
I am mother and father, but never birth or nurse. I'm rarely still, but I never wander.
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it can neither see nor feel it. What is it?
My first is second in lineอพ I send shivers up your spineอพ not quite shining bright I glitter in the light.
Just head and foot yet never tires of dancing.
What has three feet but no arms or legs?
You use it between your head and your toes, the more it works the thinner it grows.