My old college professor said something like that about Moby Dick. He called the white whale a blank screen that every character projects their own private madness onto. It made me see the whole book as a study in obsession, not just a weird sea story. That kind of key idea really does unlock the text. I keep a little notebook of lines like that from smarter readers than me.

Yeah, that "hides in plain sight" bit reminds me of a podcast I heard.

What do you do when you hit a really bad corner, like a wall that bows out a full inch in the middle? I've had to cut a gentle curve into the back of a plank before, following the wall's shape, because just adding an inch all around would leave a huge gap at the ends. It's a pain but you can't fight the room.