Answer: Trilons

Unless you’ve gone pretty deep down the rabbit hole of game show fandom, there’s something you’ve likely never considered—the design of game show boards and the fact that many of them not only have a design element in common, but that the design element actually has a name.

On dozens of game shows in the mid-to-late 20th century, you’ll find, in many forms, a nearly ubiquitous set design element: displays with triangular 3-sided rotating elements. The elements, known formally as trilons, were a critical component in early game shows. They were easy to maneuver (rotating smoothly and cleanly on camera) and they could easily display three states of information.

Although they were found on many shows like Pyramid and Family Feud, the most iconic use of the trilon was on the long running show Wheel of Fortune where they had three states: green for off, blank white for in-play but undiscovered, and illuminated with letters when successfully discovered by contestants. In the early decades of the show, the trilons were physical elements rotated by the show’s hostess Vanna White—seen here in a 1980s episode with a trilon caught in mid-rotation—but today, the physical trilons have been replaced by computer screens (a trend common across most of the entire industry).

One of the few places you’ll find trilons in use today is in advertising. When you see a billboard change its display by rotating what a appears to be dozens of little shutters until a new billboard image appears, you’re seeing trilons in action. Each billboard with such a mechanism is loaded with three advertisements, which are changed by rotating the trilons in sync to display the next image.