How do master keys work on locks?


In my experience in standard tumbler locks, they keys push pins of different heights up so that they line up evenly at a certain point so the tumbler will turn and move the deadbolt or whatever. More or less that’s correct I think. I’ve rekeyed basic home keys for people so I’ve seen the different size pins.

My question is how does a master key work that will open all of the locks? Like in an apartment building, how does one key align all the different pins in the lock…or am I missing something entirely?

I apologize if this is wrong to ask again. I read the answers and I’m still unclear. I imagine these keys pushing the pins up, but I can’t quite figure out how the key is pushing all pins of different heights up the same. I really need it explained a little simpler if that’s possible.

Thank you all so much.

In: 5

You already know how locks work. All you need is one more little bit of information.

The shear line, the cut between the pin that the key pushes and the pin that sits up in the bible. There can be multiple. Instead of just one key pin and one driver pin, you can have a third pin between them. This creates two shear lines, and so two different key cuts that allow the core to turn.

By having every single lock keyed with two shear lines, one for the “personalized” key and one for the master key, you can have a master-keyed apartment complex.

Unfortunately a half-competent lockpick can pretty quickly figure out the master key and ruin all of your nice security.

You can replace one or more of the pins with two smaller pins, so that it will open at either of the two shear lines.

Each lock is pinned to accept both the master key and the non-master key.