Lockable rotary knob M8 thread, 1 key
To lock sand plates or other attachments on the outside of the vehicle, for example.
The rotary knob must be tightened onto a nut (or other surface) for the key mechanism to work, see video. In the video, the screw is attached without threadlocker and turns easily. It is better to have 2 screws that are locked together. The key can be turned completely, one position is always closed and another half turn locked. This means you don't have to search for the closed position.

