Section lines determine what is displayed in the section results.
Section line defines the extents of the section that you extract from the building model. When you draw a straight or jogged section line through a model, every object in the model whose bounding box overlaps the bounding box of the section volume is included in the selection set although it may not display in the section result.
Once you draw finish drawing the section line, you are prompted to place the result.
After you place the section result, use Regenerate to include or remove objects from the section result. This opens the Generate Section/Elevation dialog box where you can use Select Objects to pick and choose individual objects to show or hide in the section result. Since this selection method is by per object, it does not work per style or per object type.
If you make changes to the building model after you have created the section result, select the existing section results and Refresh to view changes as applicable.