The picture show the deck cover open
My design has a full boat cover strong enough to take the full effect of the sea. The sides of the boat cover are tied to the second hole in the oar blade.
One practical benefit of this design is that it gives the sailors a fine place to store gear. That is above the oar sails and below the boat cover outside the hull. There it can rest on the oars and be lashed to the shield rail.
This space provides a great deal of protection from the elements.
Under the deck cover are the ship boats. These boats act like the roof support for the canvas boat cover.