There is a man on the video I posted above who worked in prisons having collected 600-700 symbols from females prisons, and more than 2000 common symbols from male prisons. He published a book on the subject.

He was saying that if a prisoner made a tattoo that he didn’t deserve he would be beaten up severely by other prisoners. Then given a piece brick, sandpaper and glass ordering him to remove the tattoos. Many prisoners end up in hospitals after removing these tattoos.

There is a  hierarchy among prisoners and their own code of conduct  too.