Use a 1/4”-20 screw to secure the camera to the camera tray, then put the camera on the gimbal and tighten the top bar screw slightly (if the camera has hot shoe supported).
Mounting camera has large width on the second slot of the crossbar (Sony A6000, Sony A6300).
Mounting camera has small width on the first slot of the crossbar (Black magic micro cinema camera, Flir Dual Pro R ).