1. Attach far end of string to wall or doorknob.
2. Position 3 beads about 40cm away from each other, with the closest one being 40cm away from your eyes.
3. Hold the string taut.
1. Look at the middle bead. You should see two strings as though one was coming from each eye.
2. Image formed by the left eye shows a string going through the bead at an angle to the right.
3. Image formed by the right eye shows a string going through the bead at an angle to the left.
4. When the brain puts both images together correctly, the two images seem to form an X on the string with the bead in the center.
5. Make sure you always see two strings when you focus on one of the beads.
6. If you see one string, blink your eyes, turn the room lights off and on or shake the string.
7. Train your brain to use both of your eyes and see both strings at all times.