Clockit boxes are used for synchronising the timecode on several cameras when shooting a multi camera set up. Each individual box is referenced to a master "time of day" timecode source at the beginning of the shooting day. The separate boxes then generate identical timecode for the rest of the day. Each camera is given a clockit box which sends timecode to the timecode input on the camera so that when 2 or more cameras are recording they are all using identical timecode. This timecode is also fed to an audio recorder such as the Aaton Cantar so that all pictures and sound are synchronised.