I just received my Adafruit case and it broke after the first assembly and reassembly, while trying to change my wiring access configuration. It uses bendable tangs that slip into slots in order to hold it together. Unfortunately It is made of very brittle plastic and the instructions point to warnings about being very careful while putting it together or taking it apart....which I did. I am now out $14.95 for something that cost a few cents to manufacture. The idea was good anyway because it allows the installation of a GPIO cable and the top is removable to allow for cooling as well as direct access to the GPIO pins using individual wires which is exactly what I needed. If I had access to all my tools I would build a case, but that is not an option at this point.
My Raspberry Pi Project Page: