A state of mild shock and humiliation

The prisoners who were blindfolded , put into a car and driven to the "Stanford County Jail" that has been contructed for further processing. They were brought to the warden one at a time who conveyed the seriousness of their offense and their new status of prisoners.

Then, inevitably, a series of formal procedures look like rather humiliating. Each prisoner was systematically searched and stripped naked then he was deloused with a spray to remove the alleged germ and lice. The prison was then issued a uniform. The main part of this uniform was a dress or smock which each prisoner wore with no underclothes at all times. On the smock, both in front and back was his prison ID number. 

Beside the smock on each prisoner's right ankle was a heavy chain, bolted on and worn at all times.Rubber sandals were the footwear and each prisoner covered his hair with a stocking cap made from a woman's nylon stocking.

This is not a real male prison, as experimenters said,  and their goal was to create a functional simulation of a prison to produce similar effects quickly, making prisoners feel humiliated and emasculated. Indeed, prioners started to walk and sit differently as soon as they were put in these uniforms.

The chain on the foot which is also uncommon in most prisons, was used to remind prioners of the oppresiveness of their environment. When a prisoner turne over during a sleep, the chain would hit his another foot , waking him up and reminding him that escape was not going to happen in any way.

The use of ID number made prioners feel anonymous. Each prison has to be called by his ID number and could only refer to himself and other prisoners by number. It allowed prioner to emaculate unawareness of their social identity as a normal citizen anymore.