This is a fully customizable lock. The way it works is you have a section of levers and a section of buttons. The buttons on the blue wool are numbered 1-9 and the levers are also 1-9. Each lever when in "On" position activates the button it is linked to. This means you can make the code from 1-9 numbers. Next is a "Reset" button. This button is on red wool. When this button is pressed it resets all the clocks controlling the pistons that are not controlled by levers.

Now if you wanna take a look at how it works everything is color coded.
Red: Reset
Blue: Buttons
Purple: Levers
Yellow: Door