More on AECPOLYGONs

This one would be useful for drawing details. For instance if you are detailing an inlet and you only want to draw the interior or exterior lines with out offsetting the lines this may work well.

To start type AECPOLYGON at the command line. Choose Add to draw the AECPOLYGON to the dimensions that you want. Note Dynamic Input doesn't work with this command and the since it is a polygon it has to be closed.

While still in the command type S for style and the Style Manager will pop up. Civil 3D really should have this feature:Right click on the AECPOLYGON style and choose New. Select the New style created and go to the Dimension Tab. Choose an edge width that you want (ie the wall thickness of the inlet), then choose the justification you want. It seems pretty intuitive on what they mean so I won't explain the Justify box. Press OK to exit the Style Manager.

Now that you have created the style we need to apply it to the AECPOLYGON that was just created if you are still in the command type P for Properties, it will ask you to select the AECPOLYGON and select the one you want to change. In the properties window change the style to the one you created. You should end up with a two lines going all the way around which is easier to change then two parallel polylines.