Isometric guide/ruler grid with 30° angles
Isometric guide/ruler grid with 30° angles (or as close to 30° as I could get them).
It's made of two layers - vertical guides and diagonal perspective rulers. The thought behind it was to have in one package the actual guides and a reference grid that scales nicely when zooming in.
Credit to @Steele2 for the base that I worked off of: https://assets.clip-studio.com/en-us/detail?id=1758445

(Yes, I put an actual protractor into Clip Studio to do this...)