heh... I'm watching a "That's Incredible!" reunion show and they just showed a clip of two guys... one of them laying on his back with a board with nails through it resting on his stomach (nails pointed at his stomach) and 6 layers of 1" thick concrete on top of the board, pushing the nails into his stomach.

The second guy was weilding a sledge hammer and breaking the concrete over and over. After they were all broken, the first guy stood up and showed that none of the nails pierced his skin.

The funny part? The guy weilding the sledge hammer was Do Joo Nim. A much younger, thinner Do Joo Nim. :) heh.

I took a look at the HRD website and found a video clips section:

http://www.hwarangdo.com/videoclips.htm

You can see DJN at work way back in the 1960's.