Originally posted by Scraggy_Dogg
4./ Scale the shaded area, to required size
5./ Extrude it out to wherever....
Ah-HA! There's your problem as far as the extra vertices, faces, and edges come from. Yes, you realize that you need a face to extrude from in order to create another wall section, so you extrudeto make the additional face.
The problem with doing that is that you're creating more than just a single face. You are creating four additional faces, but are only using one. (to extrude)
Here's the best way to do it:
1) Create your Cube and scale it.
2) Choose Edit Polygons>SplitPolyTool
3) Click on and edge and drag the little dot that appears to the middle of the edge. It should snap to the middle.
4) Click on another edge and place the little dot near the middle of this edge. It should also snap.
This will create an additional edge for us to work with. Snaping to the middle of the edges when you are creating the extra edge is important because it will ensure that your new edge it exactly straight.
5) Right-click, display Edges, select move tool, select edge, then move the edge to the left or right as shown in the 3rd image down below.
6) Right-click, display faces, select face, then choose EditPolygons>Extrude Face.
7) you can now extrude your face to your liking.
This gives us a clean model.