I moved into an apartment complex where the key is both unique to each apartment door, but every key can open the front door, how are both possible?

Question

I moved into an apartment complex where the key is both unique to each apartment door, but every key can open the front door, how are both possible?

In: 986

Answer 1

As far ad im aware, the pins would have 2 positions that open the door. Your key hits your first position, the master key and extra pins are all mathed out so it can fit any door.