Answer:
Lighter than feather and softer than silk, yet the strongest man in the world cannot hold me for more than a few minutes. What am I?
I am needed for most animals and hardcover books
What gets sharper the more you use it?
I stink in living but when dead smells good.
I am owned by every man, though my length differs. Their wives use me after getting married. What am I?
When is it bad luck to see a black cat?