In Revit, what feature allows you to represent 2D elements without affecting 3D geometry?

The feature that allows you to represent 2D elements without affecting 3D geometry in Revit is detail lines. Detail lines are used to create 2D annotations that can enhance the visual representation of the plan or elevation views without influencing the model's 3D attributes or geometry. They are particularly useful for adding custom detail or enhancing the presentation of drawings, such as indicating furniture layouts, site features, or other non-architectural elements.

Detail lines are typically used in drafting views or while creating detailed drawings, helping to clarify design intentions without being tied to the project’s model or impacting the real-world geometry. This distinguishes them from other features such as model lines or filled regions, which can interact with the 3D model in varying ways, thereby influencing the overall model's geometry.