Sometime around Red Belt, possibly Black Belt, you may have the Nail Break presented as part of your test. It is not about breaking a nail. By continuing to read this you implicitly agree never to try it until your sensei puts it before you to do.
What? Still reading? Okay, but I never told you to try this!
Using a pine 10 x 12 inch board, two 10d nails are hammered into the board approximately one hand-width apart, with the center of the board at the center point between the nails. The board will be suspended between two concrete blocks turned on end, properly oriented for breaking. It is a “blind set” meaning that there are no warm-ups, no practice swings: just walk up and hit it.
Functionally, this is exactly the same as every other time you break a board with a shuto (karate “chop”), except that a person’s eyes will naturally be drawn towards the shiny pointy parts of the nail tips, and where your eyes go, your hand wants to follow. Eh, there’s the rub!
My Nail Break
Having promised Sensei Mindi from when I had my orange belt that I would not under any circumstances attempt a nail break without explicit invitation, I put it on the back burner. When I got my brown belt, I remembered that the Nail Break was getting closer, so I began to prepare. The first thing I did was I got a tetanus shot. The nurse asked if I wanted the shot “because of something you did or whether it was just a booster?” I replied, “I want it because of something I might do.” She rolled her eyes as I explained about the nails and the board.
The second thing I did was set up a board with a couple of candles on it at the appropriate places. I figured that if I hit the flame with my hand the worst would happen is I would get hot wax on my hand. It worked fine, and I did not hit the candles. But there had to be a better way.
One morning I walked into the dojo with a board under my arm and a couple of crayons. “What have you got there?” Sensei Toni asked. “A crayon is just as good as a nail if you are not going to hit it with your hand anyway!” I replied. So I spent the next few months breaking 3 or 4 boards a week with either hand (because I trust my sensei implicitly, I just do not advertise what it is I trust her to do!).
As my Red Belt test approached, I bought a whole box of 10d nails and left them in Sensei Toni’s office, complete with board. At that, I had done absolutely everything it was up to me to do to provoke a Nail Break on my test. I was not disappointed. Toni approached me while I was taking the written test, showed me a board with two very real nails sticking out. I tested the width with my fist - my that is close, but I can do it.
At the appointed time during the Red Belt test I walked up to a board suspended between two concrete blocks, got myself in a proper position, and looked towards Sensei Toni to verify that she was not going to miss this much anticipated break. She nodded “go ahead,” and I looked down at the board with the nails in it: I hit it right between the nails, just as I had practiced for the last several months!
The trick to the Nail Break is to see nails when you practice with crayons, and see crayons when you do it for real with nails.
What Could Possibly Go Wrong?
One our sempai, a student (now sensei) who came before us, came down upon the nail with her hand, then quickly pulled it away with a spray of blood. On successive attempts blood squished, but she got it.
Another of our sempai (on her Black Belt test) had practiced with crayons, but only a few times. To her everlasting credit, she hesitated not at all when she came up to the board for real. She drove the nail into her hand all the way to down to the board, so that when she raised her hand the board came with it, dangling almost surreally. To this day I call her “Tough as Nails”.
Even if you break the board neatly between the nails, if you do not follow through you may get punctured or scraped by the nail points as the board snaps inwards towards its other half.
To do the most awesome Nail Break you can possibly do, there is no substitute for practice. I practiced with wooden boards, and you should certainly use real wooden boards to practice this break, but there is no reason you could not offset the expense by using a rebreakable board. I recommend using the toughest rebreakable board you can reliably break, since you do not want to come down perfectly between the nails only to bounce off of the board!
When you first start, just put a couple of pennies at a proper distance from center on the board. When this becomes routine, try drilling the center out of a checker and push a crayon or candle through it to get the crayons to stand up properly. Make a point of putting the crayons (artificial nails) as close together as possible and still complete the break. The nails will look very close together, comes the day.
When preparing for the Nail break, always do the board break with the crayons first rather than breaking a board or two for practice. Since the Nail Break is a blind set, you should always practice it in a realistic setting: practice kata for a while if you want, then try one or two pseudo-Nail Breaks with either hand.