A string walks into a bar

And asks the bartender for a beer. The bartender says "We don't serve strings here." Frustrated, the string leaves, only to return an hour later. "Bartender, give me a beer" states the string. "We don't serve strings here" says the bartender. Even more frustrated, the string leaves the bar. An hour later, the string decided to try one more time, with the same result. The string steps out onto the sidewalk, ties itself into a knot, unravels itself above the knot, and immediately returns to the bar. "Bartender, give me a beer" demands the string. The bartender replies "Haven't I told you several times that we don't serve strings?" The string looks at the bartender and says "Frayed knot."