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'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??'

She says,
'You're knot hard, you're knot in, and you're knot getting your money
back.