Introductory technical guidance for civil engineers and geotechnical engineers interested in discontinuities in rock foundations for buildings and infrastructure. Here is what is discussed: 1. INTRODUCTION, 2. ORIGIN OF DISCONTINUITIES, 3. FEATURES OF DISCONTINUITIES, 4. BOREHOLE LOGGING, 5. ORIENTED CORE, 6. BOREHOLE CAMERAS, 7. LINEAR SCANLINE SAMPLING, 8. WINDOW SAMPLING, 9. TERRESTRIAL DIGITAL PHOTOGRAMMETRY (TDP), 10. STRUCTURAL DATA PRESENTATION, 11. ROCK QUALITY DESIGNATION.