3.14 Doors barring your progress.

Should you come across a locked door you will, of course, need the correct key with which to unlock it. Typing OPEN DOOR <direction> will attempt to open it without a key; if you own the necessary key then UNLOCK DOOR <direction> will both unlock the door and open it for you. You will then be able to pass through without further ado, and perhaps LOCK the door behind you.