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Camera and photoFilm Clapperboard: Slate

How to use a clapperboard: marking the slate and syncing sound

How to use a clapperboard: what goes on the slate, how to call and clap a take, soft sticks, tail slates and MOS, and how the clap syncs sound.

4 min readBy Zarkon

On this page
  1. What is a clapperboard for?
  2. What do you write on the slate?
  3. How to use a clapperboard on a take
  4. What are soft sticks, second sticks and tail slates?
  5. What does MOS mean on a slate?
  6. Questions people ask
  7. Where Film Clapperboard helps, and where it does not
  8. Sources

What is a clapperboard for?

The Nashville Film Institute (NFI) describes a clapperboard as having two parts: the slate, where you write the information about what you are recording, and the hinged clapper sticks. The sticks were added once film included sound. On a crew, the board is usually handled by the second assistant camera, or 2AC, sometimes called the loader or clapper. The editor then uses the clap to find where each take’s audio and video line up.

Frame.io’s workflow guide explains why that works. When sound is recorded separately from picture, the editor pairs the right files by matching the scene and take information, and the clap gives a clear and precise point at which to sync them.

What do you write on the slate?

According to NFI, a working slate has spaces for:

  • Roll number: the roll of film or, on digital, the media being recorded. NFI suggests a letter for the camera followed by three numbers, starting at 001, and using “A” even with one camera in case others are added later.
  • Scene number: a number for the scene, with a letter added for each new shot. A new lens, a filter or a change from a static shot to a moving one counts as a new shot.
  • Take number: just a number. You can add “SER” for a series of takes, or “P/U” for a pickup that starts part way through.

Together, NFI calls the roll, scene and take the “Head ID”. Other spaces include the production title, date, frame rate, interior or exterior, day or night, and boxes for sync or MOS. NFI suggests taping over fields you only fill in once so they do not smudge, and blacking out unused fields.

How to use a clapperboard on a take

NFI sets out the basic routine:

  1. Stand where the camera operator tells you, so the slate is in frame and in focus.
  2. Wait until the camera and sound are running (“speeding”).
  3. Call out the scene and take. NFI recommends the NATO phonetic alphabet, such as Alpha and Bravo, for letters that sound alike.
  4. Say “Mark!” and clap the sticks.
  5. Get out of the frame straight away.

Frame.io describes the same moment from the edit’s side: once everyone is ready, an assistant reads out the slate and claps down the clapper to make a loud noise.

What are soft sticks, second sticks and tail slates?

  • Soft sticks: for a close up, the board has to be near the actor’s face, so NFI says to clap gently.
  • Second sticks: if the clap was too soft to record, clap again a little harder.
  • Tail slate: if you cannot slate at the start, slate at the end. NFI says to call “tail slate” after “cut”, hold the board upside down, clap, then turn it so the editor can read it.
  • Common mark: with several cameras that can all see the board, call “common mark” and clap once.

What does MOS mean on a slate?

NFI explains that MOS shows you are not recording audio. Circle MOS on the board, and also make it obvious on camera by holding your hand over or between the sticks, so the sticks do not come together.

Questions people ask

Who uses the clapperboard on set?

Usually the second assistant camera (2AC), also called the loader or clapper, according to NFI.

Why clap at all if the camera records sound?

Frame.io says productions often use two or three sync methods at once, such as a slate, timecode and the camera’s own scratch audio, so there is a backup if one fails.

What if a digital slate has no sticks?

NFI says to make sure you show it to the camera before the action starts.

What should I do if I am not sure what to write?

NFI’s advice is to check with the script supervisor and keep everything legible and accurate.

Where Film Clapperboard helps, and where it does not

Film Clapperboard is our Android clapperboard app: a full screen film slate on your phone. Fill in the production, roll, scene and take, then tap or swipe the sticks. The clap sound, a short screen flash and the shut sticks land together; the app measures your phone's audio delay and corrects for it, and a sync offset lets you fine tune it after a test clap. It has a tail slate mode that turns the board upside down, Next setup and Next scene buttons that put the take back to 1, and a Recents log where you can circle good takes, mark no good and add notes. The Classic Black, Indie White and Wedding Soft looks are free, and it works offline with no account. A one-time Pro unlock adds the Night Chrome, Amber Set and Forest Matte looks, a silent (MOS) clap, a time of day clock, take log export as a CSV spreadsheet and slate images without the Clapperboard mark. There is no subscription.

What it is good for: short films, student shoots, weddings and small crews where a physical board is not to hand.

What it will not do: it does not sync timecode with your camera or sound recorder (the Pro clock shows your phone's time of day), and a phone screen is smaller than a full size board, so keep it close to the lens and make sure it is readable in frame.

Questions or bugs: Email us.

Sources

  1. Clapperboard: everything you need to knowNashville Film Institute nfi.edu
  2. Syncing soundFrame.io Workflow Guide workflow.frame.io

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