The clapper, the sticks, clapperboard, slate, whatever you might call it, it is a simple tool that has become so synonymous with cinema it has become an icon.  

What is the actual purpose of the slate?

The real purpose for the slate, or clapper, is the clap you'll often hear before ‘action’ is called. The clap provides a way to sync audio and picture when they are recorded on two separate sources, later in post production they will match the peak in audio with the visual of the closing sticks on video.  This way you won't see actors mouths moving and hearing audio seconds after.    

What's all that writing on the slate?

The writing helps to keep track of important details of the production.  A lot of times an editor who never actually stepped foot on set will make sense of all of the different clips by reading important information from the slate come post production time.  On a large scale production an editor will actually have eyes and ears on set in the form of a script supervisor, they'll keep track of the good takes, the bad takes, any mistakes with the slate, and an enormous amount of additional information.  

Okay... but like what do those things actually mean on the slate?

Glad you asked!  We can look at a basic slate here-

Roll- designates the physical roll of film in the camera or in the digital-era, the card in the camera

Scene- this is the scene you are filming, this will match with the numbered scenes on the script you're given.  

Take- this is the number of takes you are currently on for that designated scene. You'll start at 1 and if an actor flubs enough lines you could make it to 100!

Prod[uction]- this is the name of the production e.g Forrest Gump, The X-Files EP 234

Dir[ector]- simply put, the name of the director, it could change if you shoot episodic television with rotating directors

Cam[era]- this is the camera operators name, you can keep track of who you can yell at if the shot was out of focus!

Cam[era]- this might not be on all slates but it's where you will mark which camera you're using or how many and which cameras you're using e.g A or A,B.  Sometimes if you are shooting special effects you can denote the lens focal length e.g 50mm.

FPS - Frames per second, how many frames per second are you recording? e.g 24, 60, 120

Date-  What's the date? e.g 02/14/15

Details- These are spread out on the bottom of the slate, you want the pertinent details of the scene to be visible, on the slate — you can cross out the ones you are not using, I usually tape over them.

INT[erior], EXT[erior]- Denotes where the scene is taking place — is it exterior or interior?

DAY, NIte -  Is it day or not when you're shooting?

SYNC, MOS -  Is there sync sound?  Or is there no sound? The Hollywood lore is abundant on this one, some say MOS came out of a German director who yelled “Mit out sound!” but it might just be for ‘motor only sync’

FILTER while not shown on that slate it's extremely common to take note of a filter if one is used in front of the lens (e.g ND.3, CPL, ProMist)

Should I use a slate for my next project?

Yes!  When used correctly the slate is a great tool to keep track of production and can be used with other naming conventions to suit the specific production needs.  The slate is a tool with many complexities and advanced techniques we didn't delve into, but when used in its most basic form it can be great to keep track of projects and a good reference to have when viewing clips in the depths of your hard drive.  

Slate Commandments

Thou shall respect thy slate

Thou shall write legibly upon thy slate

Thou shall not clap thy slate in the face of talent

Thou shall not use permanent marker upon thy slate

Thou shall know the location of thy slate at all times

Thou shall never clap thy slate when sound is not being recorded

Thou shall make sure thy slate is in frame when thine camera starts to roll

Thou shall not raise thy slate while thy camera operator is checking the frame

Thou shall make sure thy slate stays close to the camera and does not walk away!