JETPILOT wrote on Dec 2^nd, 2009 at 11:00pm:

I have never in all my years flying the 727 ever seen a plane with a "Flap 20" setting, and It isn't mentioned in Boeing operators manual. I wonder what the story is with the "20" flap setting and what the point of it is.

Beats me...but I have seen a few on Airliners.net with a "20" marking.  I wonder if only certain customers ordered them that way?!