Answer:
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
When set loose I fly away. Never so cursed as when I go astray.
What's as small as a mouse but guards a house like a lion?
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.
My tongue hangs out as I run over fields and streets all day. I get tied up every morning and untied at night.
What never gets any wetter no matter how hard it rains?