Lever Combo Lock

This combination lock is simpler and cheaper than the item frame combo lock, but it's still a neat little build.

Using a series of NOT gates (inverters), I rigged up a system that allows the door to open only when the levers attatched to the redstone torches are activated, which makes the input OFF. The final NOT gate inverts the signal, so the output is ON, which allows for the door to open.

When any other levers are pulled, the door remains shut. Useful for warding off intruders.

This lock is simpler, but it doesn't require much in the way of materials.