We also were told in boot camp that the notch was inserted between the upper teeth and lower teeth then head and lower jaw were wacked together to permanently fasten the tag between the teeth. It hurts just thinking about it 58 years later. I still cant sleep on my back because of the time I had to sleep with 35 M-1 rifles from my ankle to my neck from 9pm till 5am. All because I called my rifle a gun.