April 24, 2018

The Clapperboard and its Language

The clapperboard, or slate, is one of the most iconic symbols in cinema, yet it presents a vague notion to those who don’t know its specific use in filmmaking. Beyond its very simple, recognizable appearance, lies a more complex system which is key in the filmmaking process – and still remains relevant to this day since its invention some time around the 1920s.

What is the clapperboard and what is it used for?

The clapperboard is a device of simple construction, consisting of a small board – that is nowadays made of translucent acrylic glass, but used to be made of slate, hence its alternative name – attached to a pair of clap sticks, usually made of wood. It is held in front of the camera before (sometimes after) every take and the sticks are clapped before the action unfolds.

These elements fulfil the two main uses of the clapperboard. On the board, information about the production and each take is written, so every shot is easily identifiable by the editor. The sticks are clapped with the purpose of being able to sync audio easily in post-production, as in a professional environment video and audio will be recorded separately.

Who uses it?

The person in charge of the clapperboard during a shooting is the 2nd Assistant Camera (2nd AC), as per its US denomination, or Clapper Loader, a name that tends to be used more frequently in the UK. The job description in regards to the clapperboard not only entails operating it, but also filling out camera sheets. As part of its operation, it’s necessary to understand what to write on each section of the clapperboard and know how and when to call out the right instructions.

What to write on it?

The clapperboard is divided in different sections as can be seen in the image below.

  • Production: Name of the production
  • Roll: Identifies each roll of film, tape or media card (depending on which format the production is being shot on) the camera is recording onto. If there are multiple cameras, you will need to label the primary camera as ‘A’ camera and the second as ‘B’ camera.  Your roll on A camera could be A004 while B camera will start back at 1 such as B001.
  • Scene: Identifies the scene being shot, normally the scene number according to the shot list. (Pro tip: skip the letters “I”, “O” and “S”, as they could be confused with the numbers “1”, “0”, and “5”.)
  • Take: Identifies each take – every time the camera records and stops is considered a new take, always starting at 1.
  • Director: Name of the Director – do not misspell!
  • Camera: Name of the Cinematographer – do not misspell! – depending on the production, sometimes the letter assigned to the camera that is being used in a particular moment on a multi-cam shoot.
  • Date: Shows the date of the shoot.
  • Day/Night: Shows whether it’s a day or night scene.
  • Int/Ext: Shows whether it’s an interior or exterior scene.
  • Mos/Sync: Mos should be circled when sound is not going to be recorded, conversely Sync should be circled when sound is being recorded.
  • Filter: Shows whether filters are being used on the lens.

For the day/night, int/ext, mos/sync, most AC’s will put a piece of tape over each element that isn’t in the shot.  For instance, if it is an INTERIOR scene, then put a piece of tape over the Ext mark on the slate.  If you have any doubt to what to put on the slate, reference the shooting script as the heading of each scene will label what scene number and whether it is int/ext.

How to operate it?

The 2nd AC would normally wait until the AD calls for slate. Then, walks into frame, positions the clapperboard where it can be clearly seen by the camera (or cameras), and calls out the instructions. Once the camera starts rolling, they call out “Mark!” and clap the sticks.

When calling out the instructions, it’s very important to be familiar with the difference between the UK and US slating system.

In the UK, every single shot has its own unique ‘slate number’ starting from 1, regardless of the scene.  A new shot can be defined when the position of the camera changes, the subject or focus of the camera changes (for instance on a different character), when a lens change occurs or when any other major change happens. Take this example: let’s assume the scene order of the day is Scene 14, 27 and 6. The system would go something like this:

Scene 14, Slate 1, Take 1

Scene 14, Slate 1, Take 2

(New setup)

Scene 14, Slate 2, Take 1 – whatever the setup doesn’t affect the slate number

(New scene)

Scene 27, Slate 3, Take 1 – whatever new scene doesn’t affect the slate number

(New scene after a few slates)

Scene 6, Slate 17… and so forth – the slate never resets.

In the US however, every new scene has its own number and then each new shot has a character, that goes the alphabet, with takes starting from 1. If the end of the alphabet is reached, the letters are doubled-up (AA, AB, AC, and so on). With the same scenes as the previous example, it would look something like this:

Scene 14A, Take 1

Scene 14A, Take 2

(New setup – e.g. from Close-up to Wide)

Scene 14B, Take 1

Scene 14B, Take 2

(New scene)

Scene 27A, Take 1

(After 28 new setups)

Scene 27AB, Take 1… and so on.

In the US system, it is common practice for a 2nd AC to use entire words when reading out the slate – either using the military alphabet or made-up words. For example: “Scene fourteen alpha, take 1!” or “Scene fourteen apple, take 1!” so there is no confusion.  It is even more common that you will not use the word ‘Scene’ when calling out the shot and may simplify it to “fourteen alpha, take 1” instead.

Useful terminology and situations

  • Soft Sticks

In a situation when the 2nd AC has to clap very close to talent, they would call out “Soft Sticks” instead of “Mark” not to distract the actors.

  • Second Sticks

If they clap incorrectly, they call out “Second Sticks” instead of “Mark”.

  • End slate/Tail clap

When for whatever reason it’s not possible to use the clapperboard at the beginning of a shot (for instance if the shot starts on a high crane and the slate is not possible to be close enough to the camera), this will be held upside down first, then rotated back to its normal upright position and clapped at the end of the shot.


  • MOS

This stands for “Motor Only Shot” and it means recording without sound. The clapperboard should be held with a finger or hand between the sticks or alternatively with your hand over them when they’re shut.

  • Pick Up

When another take occurs and the actions starts halfway through instead from the beginning, the take number increases but PU should be added to the number.

  • After False Start

If both sound and camera are rolling but the take is cut before action is called, AFS should be added to the number.


  • Keep the slate as still as possible when clapping the sticks. If you move during this action, you risk the sticks not being clearly visible at a particular frame to sync the sound.
  • When the 1st AD begins calling for turnover, already have the slate in frame and ready. You will waste time and/or film or memory by not being there.
  • Try to find out where the slate needs to be beforehand.  You can do this by referencing the monitor.
  • However, don’t just stand there with the slate in frame while the 1st is pulling focus for refence marks–you will get on their nerves very quickly as they cannot see through your slate!
  • You want the slate to fill as much of the frame as possible without it being too big.  The easiest way to determine the proper place is for every 10mm of the focal length of the lens you stand approximately one foot away from the lens.  If you are filming with a 50mm lens then you should stand 5 feet from the lens and the slate will be the proper size in frame.  Knowing distance and anticipating this will help serve you as you move up the chain to become a focus puller/1st AC. Even if you live outside the US and use the metric system, it is common that lenses will still use the imperial system for the witness marks (distance from the optical plane).
  • If you buy a labelmaker it makes it incredibly easy to label things that are consistent like the production name, director, cinematographer, etc.
  • Some 2nd AC’s use pre-written tape with numbers and letters to fill out other boxes like the scene and take and borrow these from the back of the clapperboard as needed.
  • In most instances the slate should be perfectly parallel to the lens, however there are instances when lights bounce off the slate and may reflect this back into the camera. Investigate this beforehand so you will be ready and not need to adjust.
  • Anticipate changes ahead of time. While the shot is being recorded, go ahead and *quietly* erase the previous take and write the next one there.  You will then be ready for the next take if it is needed.
  • It is a best practice to plan your route away from the camera before the 1st AD calls for turnover. You may have to tuck into a corner of the set that isn’t being used or find a way around obstacles.  If you mark the slate and then panic for how to get off set or disturb a piece of the set, you will look like an amatuer or you might make enemies of other departments. Further, you should stand on the side that you will exit—if you were to walk across the frame then this is time taken instead of shooting.