AECPOLYGON's not just for architects anymore.
What is an AECPOLYGON? An AECPOLYGON is a polyline with a hatch associated with it. No while that sounds like a regular hatch it is so much more. This post will summarize the how to create them and then how to modify them.
The first thing you are going to want to do is create some AECPOLYGON styles. To create the styles type AECPOLYGON at the command line and choose the Style option. When the Style Manager comes up (yes, there is a style manager in Civil 3D, it just doesn't handle Civil 3D styles) right click on the AEC Polygon Styles and choose new to create a new style.
Now go through the tabs at the top of the style to set the settings of the new AECPOLYGON style. The picture below summarizes all of the tabs.
When the Style Override box is checked the Display Properties dialog box will pop. This dialog lets you set what type of hatch you are going to use and what portions of the AECPOLYGON should show or be hidden. The Hatching tab shown below lets you set the pattern, hatch scale, hatch angle, orientation and X Offset, Y Offset. The orientation is either global or object. The X Offset, Y Offset adjusts the hatch start point. So if you have a block wall hatch you can have the hatch start at half a block.
The Layer/Color/Linetype tab lets you assign layers to the various portions of the AECPOLYGON and determine if it is on or off.
After you have create some styles you are ready to create some AECPOLYGONs. There are two ways to create them. The first is by using the Add option. The Add option lets you draw the AECPOLYGON. The Convert option lets you take a polyline and make it an AECPOLYGON. If you use the Add option you can set the style by pressing the Style option or change it in the properties window. If you forget to change the style you can always change it in the properties window. After you create the AECPOLYGONs there are various ways to modify them. The easiest way to modify them is to select them and use the grips. The grips have some benefits over regular polylines since they have a middle grip that acts like a line grip and adjusts the connected vertices of the AECPOLYGON.
As an added feature using the Ctrl key cycles through several modifications you can do to a vertex or edge. The picture below shows the various options.
So looking at the above detail you may be thinking that you don't want the earth to have line at the portions below the surface. Well you can hide those edges and keep the top surface. To do this select the AECPOLYGON and right click and choose the Hide Edge option. Notice all of the other options you can choose.
Below is a partially completed detail using only AECPOLYGONs.
So now that you have some styles you probably want to add them to other drawings. To do this open the style manager. Go to the menu bar and choose open. From there you can open other drawings to move styles between the drawings, just drag and drop them between the drawings.
Hopefully you can see the benefits of using AECPOLYGONs. To get you on your way this drawing contains the styles used to create the detail above.