Three lengths of string walk into a bar and sit at a table. One of them gets up and goes to the bar to order drinks. When he orders, the bartender sneers at him and says, "Sorry, bud--I don't serve lengths of string." The string goes back to the table and tells his friends what happened.
"Let me try", says one of the other lengths of string. He goes to the bar but before he can say anything, the bartender roars, "Look, I told your friend already--I don't serve your kind here!" The length of string goes back to the table and tells the other two that they won't be served.
The third length of string gets up and says, "Let me try something." He goes into the bathroom and twists himself into a tangle and unfurls his ends a bit. Then he walks over to the bar and quickly orders three beers.
The bartender narrows his eyes at the string and says, "Hey, wait a minute. Aren't you one of those three pieces of string that came in here a few minutes ago?"
And the string replies, "Nope. I'm a frayed knot."