What the director said when he was typing the script, I remember it was in English, but I forgot

Generally, there are two times for slapping the slate, the start and the end.

The slate is definitely used in film shooting. Generally, when slapping the slate, you have to hold the slate and say it in front of the camera. It means "which scene, shot, action, etc. of a certain movie", which means that shooting is started at this time, and it is also convenient for post-editing synchronization when several cameras are shooting at the same time

End shooting The slate is mostly used in the recording of TV programs. This kind of slate is not as formal as the slate used at the beginning of a movie. Sometimes the director directly hits the slate with his hands and says "OK" to indicate the end