Cover on Cover is an optional, extra covering that fits select Hobonichi Techo covers to protect them from wear and tear. (Not for use directly on book.) It also provides a place to store postcards, pictures, and other decorations to spruce up the look of your cover. Feel free to fill it with family pictures, travel post cards, and other things that cheer you up!
There's an opening located in the back so you can still make use of the back pocket of your cover.