jala = net (for catching birds or fish)
dhara = bearing, supporting
bandha = bond
Step by Step
Sit in a comfortable pose.
Firm your shoulder blades against your back torso to lift your sternum. Be careful not to push your front ribs forward.
Full Jalandhara requires the chin to rest comfortably on the sternum (neck flexion). Many beginners make the mistake of only lowering the chin; in fact your chin should be met half-way by the elevated sternum.
The focus of these complementary movements is the "crook" of the throat, where the underside of the chin meets the front of the neck. Draw this crook diagonally up and into your skull (toward the top of your spine). Your head should pivot and your chin should descend over this action, which simultaneously draws the top of the sternum upward.
Work on lengthening the back of your neck, releasing your shoulders, and opening your chest in poses like Sarvangasana and Setu Bandha Sarvangasana. Never force your chin to your sternum.
If you're a beginner, don't hold this bandha continuously throughout your practice. Begin your inhalation with your head upright. Apply Jalandhara as you near the end of the inhale, hold during the retention and the exhale, then raise your head to a neutral position for the next inhale.
Contraindications and Cautions
Approach the practice of all bandhas and body mudras cautiously, especially without the direct guidance of an experienced teacher.
Avoid this bandha if you have a neck injury
Prevents the retained breath from "leaking out" of the torso through the throat
Protects the brain, eyes, and inner ears from the internal pressure of the retained breath