Meditor 

squared section tutorial
This tutorial shows how to extrude around current view axis to produce a squared section extruded mesh.
Home address for source code of meditor is: http://mesheditor.sourceforge.net

I created this tutorial to show an easy way to create squared section extruded meshes. One could notice this is not so direct as one could guess but this will void to create internal and unwanted triangles.
Create a square (this is not a box shaped mesh) as indicated in next image.
mtutor00sqsection.png
Select two points of one edge as indicated in next image. Please, notice one _must_ be in edit->vertex mode.
mtutor01sqsection.png
Use the command 'e' to extrude. Move to get same dimensions as previous square as indicated in next image.
mtutor02sqsection.png
Repeat the process to reproduce next image.
mtutor03sqsection.png
Unselect points and select other points of mesh as indicated in next image.
mtutor04sqsection.png
Extrude two times and reproduce next image.
mtutor05sqsection.png
Now change to edit->triangle mode (F3+'END') and select two triangles as indicated in next image.
mtutor06sqsection.png
Delete triangles using 'Delete' key. The resulting mesh should look as next image.
mtutor07sqsection.png
Select four (4) points as indicated. Now one _must_ change to edit->vertex mode. Use 'END' key to return to vertex mode.
mtutor08sqsection.png
Move those selected points as indicated, use 'm' command.
mtutor09sqsection.png
Change to select mode (F2) and move whole mesh as indicated in next image.
mtutor10sqsection.png
Change current view using 'd' key to reproduce next image.
mtutor11sqsection.png
Now go to command window->actions and apply the service to extrude around current view axis. I indicated in next window the button which I used.
mtutor12sqsection.png
If all worked, next window should reproduce main window.
mtutor13sqsection.png
Change zoom to see whole mesh as indicated in next image. Use '+' or '-'.
mtutor14sqsection.png
Select all unwanted points as indicated in next image.
mtutor15sqsection.png
Delete those selected points in edit->vertex mode using 'Delete' key. If all worked, next image should reproduce the main window.
mtutor16sqsection.png
I used ALT+F10. If your image looks as next image, it has wrong oriented normals. Select the mesh in select mode and use 'Backspace' key to delete duplicated. Use 'M' command to correct normals. If you see same image, use F5 to invert normals of whole mesh.
mtutor17sqsection.png
The final result should look as next image. I used middle mouse button to move world view a little.
mtutor18sqsection.png
If one notices, this process does not create triangles inside the extruded object. The extrusion process creates triangles from old to new points but does not considers transversal triangles. If one tries to extrude 4 points from a square directly, those edge in the middle of square is also extruded and that will produce an unwanted sequence of internal triangles . This follows the same idea used to create a round section from a circle shaped mesh.
That is all folks!