Continuing the discussion from Doors with Passcodes: I have a idea. What about keys?
Keys would be made in a metalwork bench using 1 iron ingot. This would make a uncut key. So go to a Craft Bench Lv3 to make a (cut) key.
By simply pressing on a door, a interface will come up showing if the door is locked or not and the power to lock door if you are the owner of the wooden door.
No one apart from admins can now enter that door.