A string walks into a bar and orders a beer.
The bartender says, "We don't serve strings in this establishment. Get lost!"
So the string steps outside ties himself into a square know and ruffles up the end at the top and walks back in and order that beer.
"Say aren't you the string that was just in here?", asks the bartender suspiciously.
The string answers, "No I'm a frayed knot."