These hand positions were developed to better reach and inflict damage or shock to the vital points, they are very specific and focused weapons using correct and various penetrating or vibrating aspects of the hands.
For this post we look at the "Iron Sword" and what was mistakenly used and taught for decades (maybe centuries), an a more buffered or muted form. Typically this is taught as a Shuto or Knife hand chop using the small finger side edge of the hand as the striking weapon. While this is effective and can be devastating, it is not the correct hand position best suited for attacking Kyusho targets.
For clarity and actual realization of this difference, first take the Shuto or edge of the hand and the target on the side of the neck called LI-18. This target is best struck down and into the neck as opposed to straight in or ascending trajectory. Once struck note the affect on the recipient, anywhere from just pain (if you missed the target or did not strike well), to a bit of dizziness and dysfunction... not bad as hitting a Kyusho Point is always better than just the neck muscles.
Now use the small bone at the end of the wrist and strike the same point in the same direction. The penetrating factor of the correct weapon on the same target will have a much more dramatic and disabling effect on the recipient. This detail is what makes the 6 Ji Hands more devastating weapons than conventional Martial Arts weapons or hand positions.
To increase the affect to an even greater degree, add the transitional action and energetic transfer the Iron Sword Hand utilizes, this will increase the effects substantially... caution, please know the neurological revival method prior to use.
Now multiply this by 6 (separate weapons), on hundreds of Kyusho Targets on the body and you will have increased your Martial Possibilities, Probabilities and Effect exponentially.
This subject is a very deep study and difficult to simply read about... actual physical use and experience under a qualified and skillful instructor is the best way of course to learn it.
However for those interested in researching and seeing the incredible affects and additional hand weapons or if they will be right for you.... we have a great video source for you to begin or further refine your knowledge and skills with. It is called "6 Ji Hands of the Bubishi" and available at this web page: http://www.kyusho.com/products/evan-pantazi/
Feel free to comment or ask a question... best of luck in your journey!