Are you looking for a way to create a cube with a cirlular hole through it? If thats what you want it's easy to do in the vertex modeler. I made one in a couple of minutes. What I did was; first create the Square. then create the circle for the hole in the same plane as the square. empty both. Next loft the square and circle. This will give you a square with a hole in it. Next duplicate the square with the hole and move it up to the desired height. The last step is to select the 4 edges of both squares and loft to connect them. Keith