How to break boards in martial arts?

There is a hand toughening and strengthening process that you can do to better insure that you don't break bones and such when doing breaking techniques. Is it necessary to do this to break a single board? Not really; however if you have to ask this then you should not be considering doing this on your own without expert supervision. You don't just use any piece of wood and there are other things also that are factors like breaking with the grain of the wood, not trying to hit on a knot, is the position of the board fixed or is someone holding it to name just a few. My first wife thought it would be easy and took a board from a group that I had sitting in a box for an upcoming demo. This was when I was much younger and really getting into breaking. So she takes this board and a couple of bricks to her speech cl since she is working on her Bachelors and is going to give a presentation on how to break a board and then finish with actually doing it. Bad idea and she came home with her hand in a cast but thought since she had watched me do it and many other types of breaks with things that it would be easy. Breaking without the proper training and proper supervision can get you or someone else hurt.