Ok, that explains things...
The Essex class had a 5 part door...the individual sections of the door could be opened, or the entire door could be opened to allow aircraft to fit. The doors themselves would travel upward beyond the posts, and the post could then be removed.
I have photos of Essex Class with the posts removed, so if you're questioning that, go ahead and open them up by removing all the posts. They would be rolled up into the ceiling of the hangar.
I have a close up photo of USS Leyte that shows this...
Jeff