Help with an Architectural Question about Vintage Paris, France

[mortalman]

This is a question that has been stumping my networks of photographers and architects, literally, around the world. It finally occurred to me that DetroitYES has a forum and a very knowledgeable readership that has always answered every question I have ever posed. Here it is in a nutshell, "This photo was taken in 1914 at 22 rue Saint-Sauveur in the 2nd Arrondissement in Paris, France. This structure no longer exists but it was part of what was known as "the old Paris". What I would like to ask someone, anyone to do is to look at this photo and notice the doorway that is to the left of center in the photo. There is an irregular shaped passageway and the doorway is right next to and to the left of this passageway. If you look above the doorway you will see a rectangular looking piece of either wood or metal that looks attached on both sides about one-third of the way down on either side of the doorway. Then it looks like it is hanging from the top down at approximately a 45 degree angle that's held by what looks like metal or some such material holding it at that angle. I hope I have explain this well enough for you to know what I am talking about. Does anyone out there know what this thing is that is hanging is and/or what purpose it serves. Sometimes these old photos and/images show us something that is either archaic or so old that it is no longer used. Then it becomes what is it? The guesses so far have been it is some sort of security device that is lowered at night to keep someone from making an unauthorized entry, another is that it is a chute of some sort that receives some i'e' bags or material from the roof and the 45 degree angle allows whatever is being dispatched to be directed into the doorway, or still another is that there is a mirror on the side of the 45 degree angled device that shines light into the space to give more light during the daylight hours. Thanks."