You study an organization. You read the rules and then look for the formal exceptions to the rules. And then you search for the informal exceptions to the rules, the unsanctioned exceptions, the "street justice" exceptions: the daily accommodations.
The accommodations are tacit understandings. If you do this, I'll do that and if you don't do this other thing, I won't do this other thing. They are part of a game in which the parties appear to be playing separate roles and yet also share a role. It is that shared role that can be fascinating. The common goal is a zone of comfort. The guard and the prisoner, the teacher and the student, the cop and the speeder, the boss and the employee - all quietly accept certain boundaries in order to avoid mutual unpleasantness. There are some things that must not be done and, in exchange for that acknowledgement of boundaries, some formal rules will be overlooked.
One of the secrets to success in organizations is knowing what is frequently overlooked and what is never overlooked. That knowledge reveals a great deal about the place.