Loops on a Grocery Cart
Those loops on the edges of your grocery cart are actually meant to hang bags that hold the more delicate items in your haul, like eggs or fragile produce. You'd think carts weren't intelligently designed, but you'd be wrong.
Notebook Margins
Lines on notebook paper serve a much more important purpose than making sure your writing is straight and your work fits inside a binder. When rats were an issue back in the Middle Ages, the lines were meant to serve as a protective border that rats wouldn't chew through.