Intake and outflow thru hulls for the head. Inside, these were controlled with Blakes seacocks, which is an older type of valve using tapered plugs. These are great seacocks that could be serviced and used for another 50 years. But I’m converting to a composting head and don’t need these thru hulls anymore. Thees thru hulls along with one in the galley were removed and completely sealed.