Three pieces of String go into a bar after work.
The first piece goes up to the barman and asks for a pint.
"Sorry" says the barman, "We don't serve pieces of String".
The second piece of string goes up to the bar and also asks for a pint.
"Sorry, we don't serve pieces of string" is the answer again.
The third piece of String says to the other two "Tie me in a knot and fray my ends". He then goes up to the bar and asks for a pint.
"Are you a piece of String?" asks the barman.
"No" says the piece of string, "I'm a frayed knot".