It is a mount for taking the picture just under
Tello. Use a mirror of 17 mm square. I refined what I made on paper on May 8, 2018.https://photos.app.goo.gl/eeST98dyfPNqscjh8 I refer to the design of Jamie-Clay.https://www.thingiverse.com/thing:2911427 I also develop TALS(
Tello Altitude Limit...