clapperboard

clap per board |ˈklapərˌbôrd ˈklæpərˌbɔ (ə )rd | ▶noun a device of hinged boards that are struck together before filming as a signal to synchronize the starting of picture and sound machinery.

clapperboard

clap ¦per |board |ˈklapəbɔːd | ▶noun a pair of hinged boards that are struck together at the beginning of filming to synchronize the starting of picture and sound machinery.