As previous posts indicate, this rifle uses an adjustable gas block and it was modified so we can interact with it externally without having to disassemble anything to switch modes of operations.
Future versions will actually use a thumb screw type connection (tool-less operation basically), but right now all it takes is a small allen-key and we can switch between manual operation and the standard semi-automatic mode of operation. All with a few turns of the gas valve screw.
We hope an even more
future version will feature a "clicking" mechanism so that the gas adjustment setting can easily be identified and set by the user without trial and error. Maybe even pre-etched values so a user can visually set the gas valve to the required setting. (Imagine if you will a channel dial on an old school TV, but much smaller obviously!)
Same photo from an previous post,