Easy to see as a visual, but I cut into the box with a dremel, and eith left the door closed or open (depending on the time of year heat/cold), when the weather turns cold in the fall/winter, I flip the position of the door and I get heat, when it warms up in the spring, I change it again and I get the A/C.... once you perform the mod once, it takes about 10 minutes to do it again with a screwdriver and some metal tape.... I posted a write up on wjjeeps.com, or maybe ju a while back I will try to find it, but it may be easy for anyone who wants to see it to just make arrangements for that and you can take a look....
I wasnt going to spend the big $$ for the dealer repair, or even the heater treater..... my plan was to eventually just attach the 2 doors together, but this is so quick and easy I haven;t bothered....
found a thread on it.... there are pics too.... my cuts were alot cleaner though...
http://www.jeepforum.com/forum/f13/temp-blend-door-fix-could-work-671134/