A string walks into a bar with a few friends and orders a beer. The bartender says, "I'm sorry, but we don't serve strings here."
The string walks away a little upset and sits down with his friends. A few minutes later he goes back to the bar and orders a beer. The bartender, looking a little exasperated, says, "I'm sorry, we don't serve strings here."
So the string goes back to his table. Then he gets an idea. He ties himself in a loop and messes up the top of his hair. Then he walks back up to the bar and orders a beer.
The bartender squints at him and says, "Hey, aren't you a string?"
And the string says, "Nope, I'm a frayed knot."