"A piece of string walks into a bar and orders a beer. The bartender says "We don't serve string here." So the string leaves the bar, makes a loop of himself, twists his ends around and through the loop and unravels his ends a bit. He goes back into the bar and orders a beer again. The bartender says "Hey! I already told you we don't serve string here. Weren't you just in here a minute ago?" The string replies, "Nope, I'm afraid not!" (A frayed knot, get it? /me sighs).