It was the age of Jazz, the Age of Intolerance, or the Age of Wonderful Nonsense, depending on whom you ask. Coolidge was cleaning up Harding’s mess. The well-heeled were boozing it up in speakeasies. And movies were finally talking.

Well, there were words coming out, even if they did happen to be totally out of synch with the lips.

This was the thorny problem facing filmmakers in the early 1920s. One device recorded visuals, one recorded audio. How do you get it all to line up?

We can’t say for sure how it happened, or where. But one day, someone, likely a grip whose name is now lost in the mists of history, had the genius idea to grab two pieces of wood—we like to think they were sawed-off remnants from a long lost set—and smack them together.

Hence, an easy marker to match.

Thus was born one of the most endearing and ever-present icons of the film and television industry. Even today, who can yell “Action!” without wanting to hear that familiar sound of the crack of the clapboard. It’s like the starting gun to every film and TV show ever made.

Unsurprisingly, like everything in Hollywood, even two boards banging together has a dramatic backstory. Years later it was claimed that the device was invented by Frank W. Thring (father of Australian character actor Frank Thring) who was head of Efftee Studios in Melbourne. All well and good, except, as it turns out, Efftee wasn’t founded until 1931, long after the clapboard became ubiquitous. So, with apologies to Mr. Thring, we’re going to stick to our anonymous grip theory.

It didn’t take long for the two board technology to evolve. Soon, black and white strips were added to the boards to make it easier to visualize the clap.

The procedure became standard almost overnight: Film rolls, sound rolls, slate is put in front of camera with important information, then boards come into frame, boards clap together, action begins.

It took a pioneering sound engineer named Leon M. Leon (1903-1998) to invent what we now think of as a typical clapboard. His innovation was to attach the slate right to the wooden strips, so the whole contraption would fit into one frame.

Clapboards, which are also called a clapper, clapboard, slate, slate board, sync slate, time slate, sticks, board, and sound marker—whew—have fundamentally stayed the same, though for awhile, it wasn’t uncommon to see an acrylic whiteboard or translucent acrylic glass instead of a traditional chalk slate. This made it easier to light so the writing would be legible.

Today, of course, slates are digital. Invented by Matthew L. Davies, who continues to hold the patent, they have a time signature or time code that matches with the code on the camera so editors can instantly and perfectly synchronize the film.

Yep, that means no more clap before the scene begins.

Kind of just doesn’t feel the same without it, right?