6.1. Grasping the Basics of Modeling with Revit6.2. Understanding Sketch-Based Design6.2.1. Floors and Roofs6.2.2. Sketching Rules of Thumb6.3. Understanding Work Planes, Levels, Grids, Reference Planes, and Reference Lines6.3.1. Work Planes6.3.2. Levels6.3.3. Grids6.3.4. Reference Planes6.3.4.1. Using Reference Planes in the Family Editor6.3.5. Reference Lines6.3.5.1. Scope Boxes6.3.6. Work Planes in a Nutshell6.3.6.1. Working with Work Planes6.3.6.2. Work Plane Visibility6.3.6.3. Other Work Plane Operations6.4. The Bottom Line