Select using intersection or union? Could somebody provide a link to the Blender documentation or another source, where (non trivial) select operations are explained? I mean performing intersection or union using all available select tools like Border or Similar.


Note: The question is not about using Border to add or remove rectangles. This is about Intersection or Union.


For example: I have selected the faces based on their material, but now I would like to keep only what is inside the green rectangle. I don't know how to do it, and I cannot find that in the documentation (currently learning Blender).



Usually graphic applications have select helpers like Intersection or Union to combine successive basic select operations. In my case I assume it's possible in Blender to intersect my current selection with a rectangle using Border.

Please don't provide shortcuts only. Using Blender 2.7. 
Thanks.
Unfortunately, selection tools don't support this directly. However, there are ways to accomplish the same result. For example:


Deselect everything (A)
Select the vertices you want to "intersect" with the previous selection. In your case, the vertices in the green rectangle.
Hide the other geometry (&#8679; ShiftH)
Do whatever it is you did to get the initial selection that you want to intersect (e.g. select by material)
Create and assign a vertex group to store the selection
Unhide everything (&#9095; AltH) and deselect (A)
Select the vertex group by clicking Select in the vertex groups  panel.




However in most cases like yours the desired selection can easily be obtained with one or two box deselections. To deselect with box select (B), use  MMB or hold &#8679; Shift when defining the box.