Its unique to the G. A pic would be useless (he is an American bully so it is destroyed) and I can not find a pic on the net. Suffice to say it is a black plastic clip that keeps the gimbal stationary when not in use. The 4K has something similar but goes around the built in camera.
Okay. Got it. That is the gimbal lock. I have the GB203 gimbal but it did not come with a gimbal lock. I suppose you could just use a couple of pieces of soft foam and a rubber band to hold it in place.