How to make knuckles hard like a brick?

Question

How to make knuckles hard like a brick?

Answer 1

Do you mean the skin on the back of your knuckles, so you can hit something and it won't hurt?

A friend of mine was into martial arts years ago (bare knuckle)and he used to lightly hit a cinder block wall with his fists until they would bleed to develop scar tissue. It took a couple years, but he was able to develop quite a layer of scar tissue over his knuckles and could hit just about anything without it hurting.