An old retired sailor

An old retired sailor puts on his old uniform and goes down to the docks once more for old times sake. He hires a prostitute named Nancy and takes her up to a room. He’s going at it as best as he can for a guy his age.

He asks, “How am I doing?”

The prostitute replies, “Well sailor, you’re doing about three knots.”

“Three knots?” he replies, “What’s that supposed to mean?”

Nancy says, “You’re knot hard, you’re knot in, and you’re knot getting your money back.