Here’s the back of the board where I glued on some other braces. The large brace (under my hand) is called the cutoff bar because it cuts off vibrations to that lower triangle of the board. At first I thought that it would be better to have a board with a large resonating area for more sound, but the opposite is true. If I didn’t brace it like this on the back, I’d get a loud initial attack that dies away way too fast. In general, the smaller the resonating area, the slower energy is transferred from the string to the air, and the longer the note actually lasts. The other smaller braces are mainly for support, but also keep that triangle from vibrating too much.