Thanks for answering, well the notion of the brick chimney is 100pc correct, a sort of square tube, In Studio Viz for instance, just to explain things better, one can create in front or top view a rectangle and can continue to create further rectangles within this original rectangle just by negating 'create new shape'. so all those subsequent rectangles form part of the same one shape.ie not new shapes
When you select one rectangle all the others get selected because its the same spline.On extrusion this forms holes.

I've just read what I've written and this seems 'trés complex'
What about if I just asked how would you go about modelling the letter O without going into text.