A German guy approaches a prostitute.
"I vish to buy zex vit you"
"OK" says the girl, "I'll charge £50 an hour".
"Ist goot, but I must varn you, I am a little kinky".
"No problem", she replies cautiously, "I can do a little kinky". So off they go to the girls flat, where the German produces four large bedsprings and a duck caller. "I vant you to tie ze springs to each of your limbs". The girl finds this most odd, but complies, fastening the springs to her hands and knees.
"Now you vil get on your hans und knees".
She duly does this, balancing on the springs.
"You vill please blow Zis vistle as I make love to you."
She finds this odd, but figures its harmless, and the guy is paying. The sex is fantastic. She is bounced all over the room by the energetic German, all the time honking on the duckcaller. The climax is the most sensational that she has ever experienced, and it is several minutes before she has recovered the breath to say:
"That was totally amazing, what do you call that?"
"Ah", says the German, "Fourspring duck technique!"
(to be correctly pronounced like that: "Vorsprung durch Technik")