Makiwara Training

A Makiwara, literally translated to "a roll of straw", is a training equipment that will take all of your punches, so you can strengthen your knuckles, fingers, wrists and arms as well as becoming quicker and more precise in your punches, so you hit where you inted to, you hit exactly with the intended parts of yours, and last but not least you hit it really hard.

Today, a Makiwara typically looks more like what you see in this clip, but in the earlier days people were actually using straw rolls, wrapped with hemp ropes. 1000 hits a day will give you a really hard skin and the punch needed to use it well.

Reference: https://en.wikipedia.org/wiki/Makiwara