def border_width=(width)
         size = width.nil? ? 0 : width
         if size > 0
            @borders[TOP] = @borders[RIGHT] = @borders[BOTTOM] = @borders[LEFT] = size.to_i
         else
            @borders = [nil, nil, nil, nil]
         end
      end
def border_width=(width)
         size = width.nil? ? 0 : width
         if size > 0
            @borders[TOP] = @borders[RIGHT] = @borders[BOTTOM] = @borders[LEFT] = size.to_i
         else
            @borders = [nil, nil, nil, nil]
         end
      end
This method assigns a width, in twips, for the borders on all sides of
 the cell. Negative widths will be ignored and a width of zero will
 switch the border off.

 ==== Parameters
 width::  The setting for the width of the border.