Mike - The blinds are basically pushed up into a plastic slot and held tight to the door with Velcro. The first picture shows samples of the parts that I used, all of which are available at Home Depot, Lowe's, etc.
The "slot" is plastic rail that is used for lattice at the top of residential fences. I simply screwed it to the underside of the metal rail of the door. The blinds themselves are 1/8" Masonite that came finished in white on one side. I painted the other side black. I used aluminum channel along the bottom edge to keep the blinds stiff. Lastly, I attached adhesive back Velcro to the blinds and the door to keep them in place.
They stay firmly in place as the door goes up an down. It takes about 15 seconds to take them all off or put them on. They work quite well and suit my needs perfectly.
The parts ...
View media item 34650
The slot ...
View media item 34651
The Velcro ...
View media item 34649