Q:

Enable Emacs column selection using mouse

How to use mouse to select column in Emacs? How to enable it? 
The emacs wiki RectangleMark says, 

there is mouse support for rectangle highlighting by dragging the
  mouse while holding down the shift key. The idea is that this behaves
  exactly like normal mouse dragging except that the region is treated
  as a rectangle.

However, when I tried it, it doesn't work. No rectangle column is highlighted. 
I don't know if I need to use the next Lisp:rect-mark.el file or not, because when I look at it, it says, 
;; If you use both transient-mark-mode and picture-mode, you will
;; probably realize how convenient it would be to be able to highlight
;; the region between point and mark as a rectangle.  Have you ever
;; wished you could see where exactly those other two corners fell
;; before you operated on a rectangle?  If so, then this program is
;; for you.

To "see where exactly those other two corners fell"? Isn't that feature already provided out of box (ref http://www.gnu.org/software/emacs/manual/html_node/emacs/Rectangles.html)? 
I'm confused. UTSL tells me that it is duplicating what is already provided out of box by Emacs. Do I need the whole rect-mark.el file, or merely the mouse key-binding part only? 
UPDATE, for the record, for all my questions, I gather all the answers to here.

A:

Here is a solution:

(defun mouse-start-rectangle (start-event)
  (interactive "e")
  (deactivate-mark)
  (mouse-set-point start-event)
  (rectangle-mark-mode +1)
  (let ((drag-event))
    (track-mouse
      (while (progn
               (setq drag-event (read-event))
               (mouse-movement-p drag-event))
        (mouse-set-point drag-event)))))

(global-set-key (kbd "S-<down-mouse-1>") #'mouse-start-rectangle)

This works in Emacs 24.4 and later, when rectangle-mark-mode was introduced.

