3D Lesson 6: Making a hole

 
If you have a wall (a paralelogram B) and would like to open a window (a hole
being another paralelogram A) on it, this is impossible using Blender.

But you can create a new object (C) being the "difference" (inverse) of A - B.
This new object C will be the wall having the window. You only need to erase A
and B...

You will see the details of this operation at this 3D lesson.

Go to:

http://www.opencroquet.org/index.php/Island_Creator/Blender_Basic_Lessons_TOC