I'm working through some 3D tutorials from a book that basically builds a bladerunner-styled sci fi blimp with a billboard mounted on it....goes through all 3D principles but in a general way.

Now, I'm trying to get a feel for the curve editing tools and am confused about something while building a simple billboard. I created a rounded rectangle in the sideview using 4 arcs, attaching 3 of them, then closing the curves. When I extrude the rectangle it looks like a fan belt with the edges bevelled. Isn't there a simple way to draw a 2D shape that's completely shaded and bevel the entire thing not just the edges (to give depth like a cube or other primitive)?