Craighill’s short breaks down two design elements hiding in plain sight: pips, the raised or sunk dots on dice and dominoes, and nubs, the raised bumps that let fingers read Braille. Then it shows their combination at work — a rounded pip seated against a matching nub forms a ball detent, the click-and-hold mechanism behind everything from socket-wrench extensions to retractable pens. Three minutes, and you’ll start seeing detents everywhere.