Answer:
When they are caught, they are thrown away. When they escape, you itch all day.
I open wide and tight I shut, Sharp am I and paper-cut fingers too, so do take care, I'm good and bad, so best beware.
In Paris but not in France, the thinnest of its siblings.
You can spin, wheel and twist. But this thing can turn without moving.
What's as small as a mouse but guards a house like a lion?
What is 9 added to any number ending in 1