Answer:
I have no voice but I can teach you all there is to know. I have spines and hinges but I am not a door. Once I've told you all, I cannot tell you more. What am I?
The more you have of it the less you see. What is it?
I am a protector. I sit on a bridge. One person can see right through me while others wonder what I hide.
What has a bottom at the top?
I have a hundred legs but cannot stand a long neck but no head and I eat the maid's life. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.