I used sand and metal shot mixed. Made it easier for thicker pipe.
Sorry, not that stuff. The flexible guard film. Like I said, the guy put it in a frame and leaned on it. Full body weight and the ball point didn't puncture it. That clear, smooth plastic you can still get for phones.
just curious, what about the clear plastic that you use as a scratch protector on cell phone screens? I was told this is a material used to cover helicopter blades for the military. The man at the cell phone store demonstrated almost impossible ability to puncture it by forcing it down over a ballpoint pen.