Above each section of the scarp's firing gallery are these: Openings, so that the commodious, choking powder smoke produced by firing black-powder weapons could be vented, and the fort's defenders could continue breathing. All American starforts have some sort of arrangement in the role of venting, and they're all just a little different. Fort Barrancas makes do with a triangular opening in the ceiling, and a rectangular opening in the wall over the firing position. Generally some sort of screen or grating was affixed to that rectangular opening, so that enemies couldn't throw old tuna fish sandwiches into the fort and suffocate its defenders with dead fish smell.