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

To add to what others said, some locks also have multiple valid cuts on some pins. Position 1 might allow a 4 or 6. Some more complex multi key systems use this along with complex rules so you might have a manager who has a key to a multiple building with a higher up manager might have a key to even more buildings. It does make it more pickable though.