A string walks into a bar and ask the waiter for a beer.

The waiter says, "I am sorry but we can't serve strings here."

The string goes home, ties himself in a knot, and messes up his hair. He goes back to the bar about an hour later, sits down and says, "Waiter, give me a beer."

The waiter says, "Hey aren't you the string who came in here earlier."

The knot replies, "No, I'm a fraid knot."