This is an adapter that clamps onto the legs of a Phantom quadcopter drone. It then allows you to attach k'nex pieces to it.
The two parts hing together on one end, and a bolt on the other end clamps it firmly into place. This does not require any modification to the drone.
It also does not foul the camera.
See a video of it working here: https://www.youtube.com/watch?v=D5rSfh1JoAw
Credit for the idea for the video goes to Jose.