Three strings come across a bar and decide they'd like to stop in for a drink. The first string walks in, goes up to the bartender and says, "Bartender, gimme a beer." The bartender looks at him and says, "I'm sorry. We don't serve strings here." Feeling dejected and a bit angry, the first string goes outside and tells the others what just happened.
When the second string hears the story, he decides he wants to give it a try. He goes in, walks straight up to the bar and asks the bartender for a beer. The bartender looks right at him and says, "Hey, just like I told your buddy, we don't serve strings here." Denied his refreshment, the second string storms out of the bar with the same story to tell his friends.
By this time the third string is getting pretty thirsty and decides he isn't going to give up yet. After thinking for a little while, he messes up his hair a bit, gets himself all twisted up, and heads into the bar. As he approaches the bar and orders his drink, the bartender looks at him for a moment and then asks, "Say, aren't you a string?"
The third string replies, "No, I'm a frayed knot."