Re-breakable boards come in different colours and thicknesses for the different levels of strength. As you would expect, just like real timber, the thinner the board the easier it is to break.
It is very important to choose the right level of board strength thickness for safety reasons and for the durability of the boards. Most adults and strong experienced users over 50kg should use the thickest board. Stronger hitters over 70kg may even use 2 boards held together. Going from one board to a double board break is a big step up in board strength so its a good idea to try 2 x 3/4 boards together first.
For small kids you should always make sure there is plenty of extra padding to protect their growing bones. You can start kids on 1/2 a thin board first to gradually build their confidence with safety. Always make sure the child does not attempt to go beyond their level as this will only serve to demoralise them and encourage poor technique if the child looses confidence and gets frustrated.
If the strikers is unable to break the board after 3 attempts then they should always go away and work on their striking technique more and have another go only when it has improved. A good rule to have for everyone when using the re-breakable boards is 3 strikes and you are out. Hitting the boards is just a good test to gauge how your well your regular training is going. Hitting boards does very little to improve your overall power and fitness levels compared to your regular training hitting a punching bag or strike pads or shield target as you are able hit the punch bag and other targets with far more repetitions in a shorter space of time. You really cannot get a proper workout hitting re-breakable boards but they are an excellent test to see if your power and accuracy is improving.
Re-breakable boards should only ever be used with the supervision of a qualified instructor to make sure the boards are held securely so they do not go flying in the air when hit and to check that the thickness of the boards are the right amount for the user. Also the correct technique is extremely important which is another reason why you should not try breaking boards without your instructor watching.
The re-breakable board only comes with a thin amount of padding so you should never hit the boards with bare knuckles. You should always use extra padding with all strikes. Wearing a boxing glove is the easiest way for the best protection of your hands when punching the boards.
Even though the re-breakable boards do eventually crack and have to be regularly replaced they still workout much cheaper than pinewoods that are only used once. Also pinewood strength is very inconsistent, some boards break much too easily and some are much harder than you would expect. With re-breakable boards they all start out tight when new then loosen up and stay the same for most of their life and then get very loose and breakdown in the end when its time to replace them. With a higher degree of consistency it is much easier to work out the degree of difficulty and strength level required with re-breakable boards which makes it a much fairer and accurate test of power particularly when used for grading tests.