Girl tied down & cut in half? Masters of illusion?

I was watching an episode of "Masters of Illusion" & they had the old classic magic trick of cuttng the girl in a box in half, BUT read all of this it's different. In this magic trick, they had an old bed that was designed for surgeries in the civil war times. The bed had straps for the girl's feet & a strap for her neck. The magician had two vollunteers from the audience to pull on some ropes attatched to the straps, leaving the woman immobile. They kept pulling on them the entire time the illusion was being done. The magician put a wooden coffin over the woman, and opened up two flaps that were on the sides to show the audience that she was still in there. The magician put the blade in one of the slots to show that it was actually touching her. Then he closed the side flaps and preceeded to put the blade all the way through, then another blade. Keep in mind that there are two vollunteers still pulling on the ropes attatched to the woman to show that she hasnt moved. What illusion was created here?