Autodesk CIVIL3D - CIVILDESIGNCOMP 2007 SLM CD Tutorials Manual page 593

Edit the elevation of a projected object
In the following steps, you will change the elevation of the tree and fence
marker so that they reflect the elevation of the corridor surface.
1 In the top viewport, click the blue marker that indicates the elevation of
the fence.
When you select the marker in the section view, notice that the blue 3D
polyline in plan is highlighted.
2 Click the grip. Drag the grip down to change the elevation of the 3D
polyline.
Exercise 1: Projecting an Object onto a Section View | 581