bricks ..more accurately 'patio slabs' is what most people use. are actually easier to break than boards in some ways. boards flex...bricks just snap. the thing is penetration, don't stop. don't aim at the brick, aim THROUGH it...just imagine hitting the floor underneath it (which you just might do lol)
i broke 4 of them very easily. use your whole body, not just your arm, and drive right through it. don't be afraid...the only time you will break your hand is if you DONT break it. it's really not so hard.