Traditionally, plot lines are thought of as 2D representations of plots. However, in Autodesk Civil 3D, plot lines can also have levels and can be used in building a grading model. Feature line editing commands are used to assign levels, including levels at intermediate points. Plot lines interact with feature lines, sharing levels at common points. They can also be added to surfaces as breaklines. When you display the plot lines, you can use the levels of the objects or you can flatten the levels to a specific level. This option is available in Site Properties.
It is not always desirable to use plot lines directly for grading work. Inserting level points, or intersecting feature lines with plot lines creates break points in the plot line geometry, which affects labels. A plot line crossed by a feature line is split into two segments with separate labels. On a small site, you could use a mix of plot lines and feature lines in your grading site, ignoring the plots that are created.
Provide greater clarity in a grading design by preventing the interaction of plot lines with feature lines, using separate sites for plot geometry and grading features. One approach is to replace the plot lines with feature lines in the grading site. There are several methods for doing this: