The yajñopavīta and its threads
The yajñopavīta is a loop of cotton made of three strands, each of three finer threads, tied with a knot called the brahma-granthi. It is worn over the left shoulder and under the right arm (upavīta).
The three strands are explained in many ways: the three debts (ṛṇa) to gods, sages and ancestors; the three guṇas; or a reminder of purity in thought, word and deed. A married man in many traditions wears two sets. For rites to the ancestors it is moved to the right shoulder, and for some rites worn around the neck like a garland.
3 strands × 3 threads · Brahma-granthi knot