Answer:
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help. Yet many people are afraid to let me help them.
I am whole but incomplete. I have no eyes, yet I see. You can see, and see right through me. My largest part is one fourth of what I once was.
What do you throw out when you need it but put away when you donβt?
Everyone has it and no one can lose it, what is it?
Though blind as well, can lead the blind well.
You use it between your head and your toes, the more it works the thinner it grows.