http://www.hinduism.co.za/sacred.htm : ...The Sacred Thread is spun by a virgin Brahmana girl and twisted by a Brahmana. The composition of the Sacred Thread is full of symbolism and significance. Its length is ninetysix times as the breadth of the four fingers of a man, which is equal to his height. Each of the four fingers represents one of the four states the soul of a man experiences from time to time, namely, waking, dreaming, dreamless sleep and absolute Brahmanhood (Turiya or the fourth state). The three folds of the cord are also symbolical. They represent the three Gunas (Sattwa, Rajas and Tamas) reality, passion and darkness, out of which the whole universe is evolved. It was done, so that the Sattwaguna or the good quality of reality may predominate in a man, and so he may attain spiritual merits. The three cords remind the wearer that he has to pay off the Three Debts he owes:

1.To the Rishis (ancient seers), 2.To the ancestors and 3.To the gods.

The three cords are tied together by a knot called Brahma-granthi, which symbolises Brahma, Vishnu and Siva (the trinity of gods, Creator, Sustainer and Destroyer). Besides, extra knots are made in the cords to indicate the various Pravaras of a particular family.

The Acharya (teacher), while investing the student with the Sacred Thread repeats an appropriate Mantra, asking for strength, long-life and illumination for the boy, the boy looking, in the meanwhile, towards the sun. A Brahmachari (student) can put on only one set of the Sacred Thread. A householder is given privilege to wear two, one for himself and one for his wife. There are different methods of wearing the Sacred Thread at different occasions. While performing an auspicious ceremony one should be Upaviti, that is, the Sacred Thread should hang from his left shoulder. At the performance of some inauspicious ceremony one should be Prachnaviti, that is, the Sacred Thread should hang from the right shoulder; and at times he is called Niviti when the Sacred Thread is worn round the neck like a garland...