Enter the purchase I made of a series of DVDs by Grandmaster Strongman Dennis Rogers. One of those amazing DVDs was How to drive a nail without a hammer. I'm going to go through some basics and tell of my undertaking of this awesome feat of strength.
At first I thought that this was going to be an impossible thing to do. My wife thought something was wrong with me. (Not sure if that has changed.)
Looking back, the biggest thing that held me back was my mind. And the fact that not many people can drive a nail through a piece of wood with their bare hand. I think anyone can do it if they believe they can. More than the little engine that could, you have to know you can. So, to help the mind out I think conditioning is the beginning of your quest to be a human hammer.
I started slapping an anvil. Sounds cool, anvil slapping. You can use any hard surface - stone, brick, wood; something to toughen the area where you'll be holding the nail. Start with soft slow slaps in the beginning and gradually build up to harder more forceful slaps. This will get your hand and mind ready for the impact of the nail drive.
Another area I noticed that was more sensitive was between the ring and middle finger where the nail protrudes. This area needed the most desensitizing. What you can do is put the nail in your palm, head of nail against the callous part of your palm, make a tight fist around the nail with the nail protruding perpendicular from your palm. See picture. Then similar to slapping, start tapping on a surface over and over to condition the inside of those fingers. Ideally the nail is driven in perfectly straight which will lessen the impact on the inside of the fingers. Now after your conditioning you will be ready to start driving.
You will need a 1X pine board, small leather pad, nails and something to set the board on. For nails, start with some small 10d or 16d nails. You can use two 8 x 8 x 16 cinder blocks for stands. Set the board across the blocks and if you want you can clamp it for rigidity. The more solid your board is the safer and more successful you will be in driving the nails in. If you have seen a martial artist break a board or other feat similar, you will notice the focus and intent in their eyes. The same applies to nail driving. You must focus and be intent on putting that nail through the board. At first I noticed myself holding back when I was driving. You have to break the mental barrier and let yourself see the nail go through the board.
Arm motion when driving is like reaching back with nail tightly fisted and throwing your hand on top of the board. I've also seen straight arm in front of you, raise up stiff arm palm down and blast nail through that way. Remember to lower your whole body on impact of nail that will give you more power and keep you from holding back and falling short on impact. Once you're driving the small nails through the 1X pine board with ease then move up in nail size and start over. At one point I knew I was ready to move up - I had driven the smaller nail through the board so hard that I broke the board after driving the nail. That will make the fingers a little sore.
Nail driving is a dangerous hobby, so exercise precaution and don't be in a hurry. I will promise that if you put in the time to learn this lost feat, after you accomplish driving a nail with your bare hand it is very impressive and pleasing to the general public.