The curve from surface projection operator will help you extract curves from vertical surfaces. These curves are often helpful for creating 2.5D features from surface or solid models.
If you are not trying to extract curves from drafted features, you can set both the Wall angle and Elevation to 0 and click Next. If you want to extract the cross sections of drafted features follow the steps below.
If you want to extract curves from drafted surfaces, you will need to set a Wall angle. If you know the angle, type it. If not click on the Wall angle label. The dialog box will warp out of the way. Click two points on the same vertical isoline as shown here. The dialog box returns.
For the Elevation enter the Z coordinate of the top of the feature or click on the Elevation label and click on the top of a wall of the drafted surface
Click Next.