An old sailor hires the services of a prostitute.
He's soon going at it as well as he can for a guy his age, but needing some reassurance, he asks, "How am I doing?"
The prostitute replies, "Well old sailor, you're doing about three knots.
"Three knots?" he asks, "What's that supposed to mean?"
"Well," she says, "you're knot hard, you're knot in, and you're knot getting your money back.
He's soon going at it as well as he can for a guy his age, but needing some reassurance, he asks, "How am I doing?"
The prostitute replies, "Well old sailor, you're doing about three knots.
"Three knots?" he asks, "What's that supposed to mean?"
"Well," she says, "you're knot hard, you're knot in, and you're knot getting your money back.