"No problem", says the prostitute.
So off they go to the prostitutes flat where the German produces 4 large bedsprings and a duck whistle.
He says " I vant you to tie ze springs to each of your limbs"
The prostitute thinks he's a complete nutter, but goes along with his request and ties the springs to her hands and knees.
"Now you vill get on your handz und kneez" says the German.
The prostitute obliges and balances on the springs.
"Now you vill pleaze blow ze whistle as I make love to you."
The German drops his trousers and does the business.
The sex is fantastic, she is bounced all over the room by the German, all the time she is blowing the duck whistle.
The climax is the best she has ever had and its several minutes before she can get enough breath back to say "That was amazing, what do you call that?"
The German replies " Four sprung Duck Technique"