Enter picture mode (ESC-x picture-mode)
- Go to top left corner, press CTRL-Space.
- Go to bottom right, press CTRL-x-x (This selects the rectangle)
Working on rectangle
- Press CTRL-x-r-k to kill the rectangle (and make it available as 'last-killed-rectangle')
- Press CTRL-x-r-d to delete the rectangle
- Press CTRL-x-r-y to yank 'last-killed-rectangle' with its top right at the mark.
Press ESC-x-clear-rectangle to fill the rectangle with spaces.
Finally quit the picture mode with CTRL-c-c