A Glock switch is a small device that can be attached to the rear of the slide of a Glock handgun, changing the semi-automatic pistol into a machine pistol capable of fully automatic fire. Glock does not manufacture switches to be attached to their firearms, nor do they design their firearms with the intent of having machine gun conversion devices installed. They are aftermarket parts manufactured and sold illegally through the black market or made at home using a 3D printer.