 On the butt side of the hinge are the trigger, camera screen (which is on a horizontal hinge just like the mid-gun hinge but it is off of the left side of the gun), and controls for the camera and light.The periscope rifle was independently developed by a number of individuals as a response to the trench warfare of World War I; they were used by armies of several countries from 1914 onwards.This earlier idea was simply a specialised "second" stock and trigger mechanism combined with a periscope to allow the shooter to remain safely "within" the trench and still aim and fire a rifle that was laid over the top of the trench parapet.