Answer:
What has a head and a tail but no body?
I hold two people together but touch only one.
I am a protector. I sit on a bridge. One person can see right through me while others wonder what I hide.
Without me everyone would lose their head.
I start with T end with T and within me is T.
Runs over fields and woods all day. Under the bed at night sits not alone, With long tongue hanging out, Resting at your feet until we go for a walk