As prisoners were not allowed to be photographed as identifiable, guards dressed as inmates were used for extras.
The 100 members of the cast and crew used for filming inside the prison had their mug shots taken as part of the special security measures taken during production.
The make-up crew members used Vaseline during the shooting, for the hair, and they noticed that some vaseline regularly disappeared. It appeared that it was the real convicts who used the Vaseline for sexual purpose.