I was putting this together for myself then realised it would be a useful addition to the resources page.
It’s simply harmonica diagrams but instead of note names, I’ve put the scale degree’s for each of the three chords in the 12-bar blues. This is extremely useful information and something you’ll want to start memorising over time. However, if it makes no sense to you, don’t worry. That just means you haven’t yet learned about scale degrees.
An in-depth explanation of scales and scale degrees is a topic for another day but if you want to know more you could do worse than check out my (long neglected) Music Theory for harmonica players series.