The stocking cap on his head was a substitute for having the prisoner's hair shaved off. The process of having one's head shaved, which takes place in most prisons as well as in the military, is designed in part to minimize each person's individuality, since some people express their individuality through hair style or length. It is also a way of getting people to begin complying with the arbitrary, coercive rules of the institution. The dramatic change in appearance of having one's head shaved can be seen on this page.