In 1985, the Innovative Design Fund placed an ad in Scientific American offering up to $10,000 to support clever prototypes for clothing, home decor, and textiles. William Freeman Ph.D., then an electrical engineer at Polaroid and now an MIT professor, saw it and submitted a novel idea: a three-sided zipper. Instead of fastening pants, it'd be like a switch that seamlessly flipped chairs, tents, and purses between soft and rigid states, making them easier to pack and put together.
it’s so you can get both balls caught in the zipper at the same time! I’m not sure though as I didn’t read the article