This was designed for the Mini NES Raspberry Pi Case by daftmike. This was made to be used in conjunction with Evan Wright and Jared Kirchgatter's Pi Control Boards. It plugs into the top right USB port of the Pi3. This helps brace the Front Panel when you push in the Power/Reset button.

I recommend 25% infill.

EDIT: I shortened the USB part so you should be able to insert/remove it now without having to remove the Pi 3 from it's case.