Hark! Adventurers approach!
I only know what those door-within-a-door things are called because I specifically went to look it up. At first I thought it might be a “sally port”, but that proved not to be the case.
As an incidental point, I’ve added a handful of social media buttons to the comic posts – if you could +1, share, like, tweet or whatnot to spread the word I’d be very grateful. 🙂