These are the 3 Entrances to the SafeZone, which apparently need monitoring. It is Sewers Entrance, Dead End Entrance and the entrance through which the cat passes into the Slums. They are all from different sides of the Slums. There is no fourth entrance, as the Slums are bounded by a wall on one side.
Entrances monitors are paid two pints of Syuba Oil per day:
Announcement:
Looking for someone capable of monitoring the southern entrance to the SafeZone. The remuneration is two pints of Syuba oil per day.
Please Contact the Guardian.-- B-12, reading a sign in the Slums
This reinforces what we learn from Azooz: that the economy of the Slums is based on a barter system.
It also tells us that the Guardian is not the only person guarding the Slums against the Zurks; there are others, out protecting the safe zone, and the Guardian organizes these security forces.