Answer:
In Paris but not in France, the thinnest of its siblings.
What kinds of men are always above board?
It can pierce the best armor and make swords crumble with a rub, yet for all its power It can't harm a wooden club.
I weaken all men for hours each day. I show you strange visions while you are away. I take you by night, by day take you back. None suffer to have me, but do from my lack.
What moves without seeing and cries without eyes?
You use it between your head and your toes, the more it works the thinner it grows.