What Am I Riddles

Question: What fastens two people yet touches only one?

Question: What has 3 feet but cannot walk?

Question: What is brown or silver, has a head and tail but no arms or legs?

Question: What is black when you buy it, red when you use it, and gray when you throw it away?

Question: I run over fields and woods all day. Under the bed at night I sit not alone. My tongue hangs out, up and to the rear, awaiting to be filled in the morning.

What am I?