Thanks for the link, now I get how it works. May end up needing to replace a blend door on my 2010 Silverado and not looking forward to ending up like the photo above.I was 'inspired' to make it by this store bought unit.
I know it's not that expensive, but I needed a project to do. I made it out of materials on hand. I don't have sheet metal bending capabilities to make something as small as the housing, so I resorted to milling what I needed out of flat stock, machined the wheel out of a hunk of brass, and used low-temp silver solder to hold some of the parts together, and one screw to hold one end in place.
Amazon.com has the "Handee Clamp" as well.