Poonool (also spelled Poonul) is a sacred cotton thread worn over the left shoulder and under the right arm by Hindu men.
The Sri Vaishnava (Iyengar) tradition has specific rules for this thread. It represents spiritual growth, purity, and a lifelong commitment to Vedic studies and religious duties.
The term "Poonool" means "flower-like thread" or simply "holy thread". In Sanskrit, it is called Yagnopaveetham.
Sri Vaishnavas wear a poonool with two knots (unlike other traditions that use three). These knots are called the Brahma Granthi or Brahma Mudi.