Choose thin, smooth board for chopping, such as slim pine boards. Don’t try to chop anything that is too thick or hard (3" maximum is suggested to start). A cinder block may be possible if you have been training for a few weeks and yell very loudly when making contact.
Imagine your hand going through the wood or brick. If you can’t see it happening, chances are it won’t happen. This could be bad if it doesn’t. Remain positive. Be one with the chopping motion.
The edge and heel of the hand can take quite a lot of force provided they are the parts of your hand that contact with the wood. However, as a learner, it is best to have someone mentor you or, if that is not possible, to bring down your hand gently and with repeated practice, increase the force. If you feel great pain, stop for the day. If any serious damage to your body has occurred, see a doctor immediately.