In plan views (such as floor plans and ceiling plans), you can define grid lines that are arcs rather than straight lines. Arc grid lines will display in section views where the center of the arc intersects and is perpendicular to the section line.
For example, the following floor plan shows 2 arc grid lines. Grid Line 3 intersects the section line, but its center is not perpendicular to the section line. As a result, Grid Line 3 does not display in the section view. Grid Line 2 intersects the section line in the floor plan, and its center intersects the section line perpendicularly. Therefore, Grid Line 2 displays in the section view, indicating the center of the arc.