According to legends, in the Vamana avatar, Lord Vishnu pushed King Bali into the underworld. It is believed that he tied a red thread on the wrists of Bali, to grant him immortality. That began the practice of tying a red kalava on the wrist of people, to grant them long lives. When Kalava is tied on your wrist, it should always be done with your palm facing up, never with palm facing down and there are always three knots tied. Inside your wrist, more towards the side of your palm are three veins, or naadis, as we call them popularly. Each of these naadis is associated with the three bodily doshas or constituents, viz. vata, pitt and kapha." "Vata or vayu, the impulse principle necessary to mobilize the function of the nervous system. Pitt or bile, which is useful in digestion and supply of blood and energy to various parts of the body. Kapha or phlegm, the carrier of nutrients into the arterial system. So, tying three knots, the kalava creates enough pressure on these naadis, each to keep your body free of any disease related to these three constituents.