Answer:
I am a protector. I sit on a bridge. One person can see right through me while others wonder what I hide.
I hide but my head is outside. What am I?
What insect does a blacksmith manufacture?
I can be short and sometimes hot. When displayed I'm never cold. What am I?
I destroy your home from the inside out.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?