And since we're staring out a firing embrasure, let's have a look at those Totten Shutters! Designed by the American star of the Third System of Seacoast Fortification Joseph Totten (Simon Bernard, the Frenchman who designed a huge number of US seacoast forts built in the first half of the 19th century, was the star), these heavy iron shutters would be blown open by the gases emanating from a cannon's barrel ahead of the projectile with each shot. They were so precisely balanced that they immediately swung back shut, and automatically locked. Many examples of these shutters still sit, majestically rusting away, in place.