Answer:
I am mother and father, but never birth or nurse. I'm rarely still, but I never wander.
Lighter than what I am made of, More of me is hidden Than is seen.
Only two backbones and thousands of ribs.
What I am filled, I can point the way. When I am empty. Nothing moves me. I have two skins. One without and one within.
As a whole, I am both safe and secure. Behead me, I become a place of meeting. Behead me again, I am the partner of ready. Restore me, I become the domain of beasts.
What covers its face with its hands, speaks no language, yet most known what it's saying?