What is always in front of you but can’t be seen?

What is the difference between a jeweller and a jailer?

What does this Rebus Picture mean?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

Samuel was out for a walk when it started to rain. He did not have an umbrella and he wasn't wearing a hat. His clothes were soaked, yet not a single hair on his head got wet. How could this happen?

What does it mean?

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

What does this say?

XLR8

A wealthy man lives alone in a small cottage. Being partially handicapped he had everything delivered to his cottage. The mailman was delivering a letter one Thursday when he noticed that the front door was ajar. Through the opening he could see the man's body lying in a pool of dried blood. When a police officer arrived he surveyed the scene. On the porch were two bottles of warm milk, Monday's newspaper, a catalog, flyers, and unopened mail. The police officer suspects it was foul play. Who does he suspect and why?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?