An old retired sailor puts on his old uniform and heads for the docks once more for old times sake.
He engages a prostitute and takes her up to a room.
He is soon going at it as well as he can for a guy of his age, but needing some reassurance, he asks, "How am I doing?"
The prostitute replies" "Well old sailor, you're doing about 3 knots".
"Three knots?" He asks, "What's that supposed to mean?"
She says," You're knot hard, your knot in and you're knot getting your money back.