It was a vertical version of the magical illusion
of sawing a woman in half, except the
woman's midsection was removed.
Magician Robert Harbin invented a trick he called the Zig-Zag Girl, which he first presented in 1965. The illusion was widely performed by other magicians. In fact, it may be the most copied stage magic illusion in history.
Why did it become so popular? It fit the performing requirements of the time. It was deceptive and could be done with the audience on all sides (what magicians call "angle proof"). It could also withstand the close scrutiny of television, be done silently or with talking, and it required only the magician and one assistant to perform. Finally, it was relatively cheap to buy or make.
(And there was little that magicians could do to prevent others from copying a trick like this, and they did.)
Yet, as other magicians performed this illusion, many of the little theatrical touches that made it so great, that "sold" the illusion to the audience, were dropped.
Watch Robert Harbin perform his invention in 1970, as he introduces it as "the great carve-up." (Skip ahead to 27 seconds to avoid the introduction.)
The Zig-Zag Girl Illusion by Robert Harbin