This breath balances the left and right sides of the brain, and the left and right energies (Ida and pingala nadis). It is also good for sinus, stress and headaches.
To practice, place the thumb over one nostril, the first and second fingers on the eye brow centre or tucked under the nose, and the fourth finger over the other nostril. Block right nostril. Breathe in through left nostril. Block left nostril, breathe out right. Breathe in right, blocking left, breathe out left, blocking right for 30 rounds.
If you have a blocked nostril, this breath will clear it, but to help, make a fist with the hand on the side of the blocked nostril and place the fist under the arm pit of the opposite side until nostril clears.