An old retired sailor puts on his uniform and goes down to the docks once more for old times sake. he hires a prostitute and takes her up to a room.
He's going at it for ages as best he can for a guy of his age and asks "How am I doing ?" The prostitute replies, "Well Sailor youre doing about 3 knots."- "3 Knots?" he replies, " What's that supposed to mean?".
She says" Your knot hard, your knot in, and your knot getting your fu**in money back !