Sweep

The Sweep tool is similar to the extrude tool in that it can turn a 2D object into 3D by giving it height.  The sweep tool is much more versatile though, because you can sweep along arcs and splines or lines that are angled.  This gives you much more flexibility than a simple extrusion, which can only be done straight at a  90 degree angle.

To use the Sweep tool, first select which items you want to sweep in order to create the new object.  These items will be the "cross-section" of the object after the Sweep command is done.   After you have selected everything, choose the line along which you want to create the Sweep.