On the Mercedes-Benz W124/S124 wagon, a small plastic clip holds the bulb holder inside the rear tail lights. After years of bulb changes, the clip fatigues and snaps, and the bulb holder falls out, leaving the tail lights dark. No replacement existed, so I designed one. After 10–15 prototype iterations to get the fit and “click” just right, I sold over 100 clips to owners around the world.