About Feature Lines
A feature line represents an object in the drawing from which you want to grade, such as a swale or a ridge line.
About the Feature Lines Collection (Prospector Tab)
Use the Feature Lines collection in the Prospector tree to manage feature line styles and layers. You can also view feature line information, such as length, elevation, and grade.
About Creating Feature Lines From Objects
You can create a feature line by converting existing 2D or 3D polylines, lines, or arcs. You can select objects in the current drawing or from an Xref.