The idea behind is that the circular bars are sharing the focal point with the reflector. It means that in every position the parabolic will have the same focus point. You don't need to change the position of the cooking pot, just push the circular bars up and down. The two wheels on the frame serve to turn the device around. One idea is also to connect the support for the cooking pot to the frame. In this model you would also have to adjust the stand for the cooking pot as you turn the frame around.