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