Clapperboard, used in film production to aid synchronizing audio and video and to identify different shots
The clapper (two sticks hinged together) has been anachronistically claimed to have been invented by Frank W. Thring (father of actor Frank Thring), who was head of Efftee Studios in 1930s Melbourne, Australia, however as Efftee wasn't founded until 1931, not the 1920s as sometimes stated, this claim must fail.
Dropping out in 1932, he started working in the film industry at Wembley Studios as an unpaid gofer for Michael Powell, among others, eventually graduating to the positions of clapper boy and camera assistant on quota quickies.