Velcro works by having two strips of material, one with lots of tiny hooks, and one with lots of thinner loops that the hooks can cling to when the two elements are pressed together. This mechanism of sticking was inspired by the way tiny hooks on the seeds of burdock, known as burrs, attach to animal fur and human clothing.
The hooks and loops in Velcro are commonly made from nylon and polyester with the hooks being more rigid and thicker than the loops.
The more hooks and loops that are attached per unit area, the stronger the bond with heavy-duty Velcro containing up to 400 hooks and loops per square inch. In some cases a five-centimetre (two-inch) square piece of Velcro is enough to support a 79-kilogram (175-pound) person.