Answer: A Waffle Iron

One model of early Nike shoes were known as Waffle Trainers and for good reason: not only did the sole resemble a waffle iron grid, but the waffle iron itself was an inspiration for Nike shoes in the first place.

As the story goes, Nike co-founder Bill Bowerman began tinkering with mixtures of rubber and latex to create grippy soles for athletes and give the runners he coached at the University of Oregon an edge. Inspired by the design on his wife’s waffle iron, he sacrificed the iron to make molds for shoe soles that were both grippy and had protruding nubs on the bottoms (much like the waffle iron has protruding iron nubs to make the little pockets in waffles).

The combination proved more than ideal and the running shoe was forever revolutionized and runners the world over now wear shoes with soles inspired by the grid of a waffle iron.