In my video “CD Signal Mirror In Emergency” I illustrate the method of aiming the suns’ reflection off of a CD much like using the “bead and trough” or “peep sight” of a gun. By extending one arm with two fingers held up in a “V” position while a mirror is held next to your eye to reflect the sun at the bottom of that “V”, you can aim at your target between your fingers. I further describe in an article “Signal Mirror Target Practice” the importance of practicing this method. Much to my delight I had a comment to that article from a viewer who described his method as follows: “…If one is using a CD mirror, there is a way to mimic a WWII signal mirror sight with two CD’s.
1) Place two CD’s back to back.
2) Aim the CDs near the general direction of the sun.
3) Look at the reflection of your face in the back CD. You should see a spot of light corresponding to the CD hole.
4) Move the CD so that the reflection of the spot of light appears to be directly over the actual CD hole.
5) Look through the CD hole, and while keeping the spot of light in the hole, look directly at your target.
If both things are lined up, the sunlight will reflect toward your target.”

I decided to try this method out for myself. Sure enough it works. I noticed some things that you might find helpful. While holding the CD in my hand I noticed that the light coming through the hole created a bright spot on my hand which in turn reflected as a refractive line on the backside mirror. I could shift my hand left or right to center the line over the hole. I could then shift the CD up or down to center the reflected dot into the hole. I used a reflective license plate as a target so that I could see when the light passed over it. The short video above captures my test results.

I have included a photo of a retro-reflector mirror for reference to this signaling method.