Yeah, the face holds the buttons in. Doesn't the face accomplish this by a slight change in hole width between the inside and outside of the face, having the outside (showing) be smaller? Then, the tiny jibs on the buttons lock in place with the smaller hole of the inside of the face. Isn't this how it works?

That's why I'm wondering: like someone else mentioned, the bottom hole looks triangle. How is it holding the button in place?