“In the papers, in those days, they’d print pictures of where murders occurred and they always wrote ‘X marks the spot’ where the corpse was. So we used Xs all through the film. When anyone connected with the picture thought up some way of using an X, I’d give him a bonus.” — Howard Hawks to Peter Bogdanovich
The X-es are so obvious I can’t believe people wouldn’t perceive it, even if they didn’t know this backstage story.
If there’s an X on the screen somewhere, you know the character is dunzo.