It is a TV/Movie cliché: the wall covered with pictures, maps, documents all connected with string or yarn, usually red (so it shows up on camera I suppose) to signal that something big is going on. TV Tropes call the cliché “String Theory.” There are usually two situations where we see such walls depicted. The first is the detective drama: it is posted on a whiteboard in the middle of the squad room so our characters can stand around it do some plot exposition. Another detective drama trope is when our hero has been taken off the case by the captain because he’s gone rogue one too many times. Our detective goes home and, to the surprise of no one, there is a wall covered with all the clues connected with the obligatory red yarn.
The other situation is more ominous. The wall is being constructed by the bad guy. Maybe a serial killer, maybe someone who has lost control of their faculties. String theory has now been transformed into a “Crazy Wall” Crazy walls are usually signs of conspiratorial thinking. Someone who is convinced that some evil person or group is control of the whole situation and must be unmasked. Someone who thinks the world is controlled by Colonel Sanders and his friends. The Crazy Wall signals to the audience that there is an unbalanced mind at work:
The trick for the audience is to try to figure out if the character is onto something or has gone off the deep end.
The Crazy Wall has always annoyed me as a lazy bit of writing. Maybe it is because I’m not a very visual thinker, but I’ve never understood how the wall was supposed to help the character figure things out. Maybe it is because I’m not very crafty and I could never figure out how that yarn always looked so tidy. And you can forget about your damage deposit what with all those thumbtack holes in the wall.
So I never saw the use of such a wall. Naturally, now I’m working on a Crazy Wall of the Alt Right.