I had some 1/8" MDF lying around from barricades that I had made to keep the dog confined to the kitchen when I had to leave him alone at home. Poor dog.
I made a small improvement on the original in that I beveled the sliding members so as to provide a sort of a lock. It can comfortably accommodate panels ranging from 6" to 11" height
Lynda was impressed and I got me some brownie points.....
With a 7" x 7" panel in place
With a 8" x 8" panel in place
Close-up showing the beveled support
Close up showing the beveled support and sliding member