Answer:
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
There are 30 cows and 28 chickens. How many didn't?
You can hold it without using your hands or arms. What is it?
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.
What has two hands, a round face, always runs, but stays in place?
What covers its face with its hands, speaks no language, yet most known what it's saying?