PDFs
Browse hundreds of .pdf diagrams on GitHub.
Fretboard Diagrams 2023 by Chris Adams — an open source (free) collection of PDFs for all types of guitar scales.
Perfect Fourths Scale Guide
Scale positions in perfect fourths tuning.
Perfect Fourths Transition Guide
How and why to switch to perfect fourths tuning.
Triad Studies Quick Reference
A compact triad reference for daily practice.