Close up of top, inside of door assembly. White on far right is the south end of the enclosure's arched-shape wall that holds the panel door. The four door panels can be seen, three of which that have the small blue squares that act as stops for the next door panel as it raises up.
 
 

 

 
 

Left: inside view of the door in the open position. Note the notched and recessed side rail. Each door panel has a lowered, notched stop that not only keeps the door in place but also acts to stop it from lowering any further.

Right: profile image to show the angle of the door. This is neccesary to allow the light blue-colored door panels to raise up and behind the white arched wall.