My buddy at a welding shop had a similar thing with a finger-tap code for different metal grades. It confused their new hire for months until he saw it used during a big rush order. @hugo_scott, your paint spill signals remind me of that, how these silly things just stick. When the kid finally got it, he said it felt like he was really part of the team.

Ugh, tell me about it, @jenniferlane. They really do mark everything up so much. Finding another source feels like the only way to fight back.