A note that maybe of some interest is that you can read about Mr. Castle (and his extensive background) on his website.
http://www.sabretactical.com
Also of interest may be the video section showing Mr. Castle using this technique:
http://www.sabretactical.com/Video_C...deo_clips.html
FWIW.
Regards,
HS/LD
(I didn't know anything about this guys until yesterday)