How does Velcro stick and unstick?

Velcro sticks because one strip has tiny hooks and the other has tiny loops. When pressed together, many hooks catch many loops, making a hold stronger than any single catch. It unsticks when you peel from an edge, freeing the catches one row after another.

The idea came from burrs, the clingy seed cases that grab fur and clothing outdoors. Under magnification, their hooks showed how a fastener could copy nature’s trick. That scratchy tearing noise is countless small releases happening almost at once, rip.