Whats that thing directors use ? ?

Question

when directors are directing movies they have that black and white square thing and at the top you can pull up a piece then they slam it down and say action

whats that called!

Answer 1

It's called a clapper; it is used to make a sudden sharp sound so that the sound engineer can synchronize the sound recording with the film.

Answer 2

It's a clapper or clapboard.  And the director doesn't use it, the person who operates it is called the clapper loader.

Actually, these days the "clap" function isn't always used, what the the advances in audio-visual synchronization.

Answer 3

It's called a clapboard, used in films to help line up the sound with the action.