When you enlarge the pic it looks to old eyes that it is fastened with screws from the top. Besides what you bed with, I always put epoxy in screw holes before driving the screw. That way water can't seep down the threads and rot the wood. Usually people replace screws over time with bigger or long screws over and over. With epoxy it's done the first time and holds better.
I would use Black Loctite PL S30 roof and flashing polyurethane. It is like 5200 but softer, so it can come apart. I have it so would use it and it is cheap.