Top Hung Rolling Door Bracket

[Frank S]

the 30" gap is the easy part just hinge a drop down with large cane bolt locks on each end the leaf could be hoisted up to lay against the door by a windless or spring system like that of a garage door mounted on the door itself so it moves with the door, make the drop leaf out of barn wood if you wanted
I've done similar at a business in ST Louis many years ago the building was the old Carter carburetor factory the door may still be there