With the release of B-Mesh with Blender 2.63 a lot of old Add-ons needed to be updated in order to work with new mesh system. Fortunately some really useful add-ons that are not updated on a regular basis still work with B-Mesh really well. One of my favorite add-ons for architectural modeling with Blender is TinyCAD. It is a simple, but powerful polygon modeling tool, because it let us work with edge intersections in Blender. To visualize all that this Add-on can do, visit the thread at the Blenderartists forums where you will find a description of how TinyCAD works.
And if you want a practical example, here is a quick demo video showing how we can cut intersections of two planes using the add-on:
It works really like a CAD tool, and fortunately we still can use it with Blender 2.63.
CAD is using for designing of building,machinery and many other things.It brought a new revolution design and construction world. Because it makes the more clarify the picture or diagram with correct dimension.