An old retired sailor puts on his old uniform and heads to the docks once more for old times' sake.
He engages a prostitute and takes her up to a room. 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 3 knots'.
Three knots he asks,
'What's that supposed to mean ?'
'You're knot hard, you're knot in, and you're knot getting your money back