The attack is most often telegraphed. As soon as the weight shifts, you should already be moving in to block. Second, each block should essentially be a strike. A block is an aggressive tactic, not a passive one. For that reason, you will not block with weak points of the body.
Every block has the maximal stability and power needed to stop a strike.
Additional principles and areas to be covered. Learn how to destroy an assailant and get back to your feet before his buddies stomp your skull or soldiers start cheering you on for best field wrestling match. Using a neon tiger striped gi and a lot of yelling, acrobatics and theatrics.