A couple of possibilities:
1) Create a flat 3dmesh with Draw>Surfaces>3dSurfaces>Mesh with its
corners at the corners of the courtyard. In plan view, stretch each
vertex using the .z filter to set the z-coordinate of the vertex to the
elevation of the nearest contour line.
2) Since (1) is a pain, try LV.LSP, which I have just re-posted to the
autodesk.autocad.customer-files newsgroup. To use it, you will have to
explode your contour lines into line segments, so make copies first. It
creates a mesh more or less "draped" over your contour lines. Some guys
in the Philippines wrote it. Read the notes at the top of the file.
> I am having trouble trying to figure out how to apply a 3d mesh or face. I
> have a 152' x 36' courtyard that i need to apply a mesh so I can show the
> contour in 3d. I have the contour lines already drawn as ploylines and I
> have located them at the right elevation. What should I do and how do I do