Gau are amulets made of precious metals and gemstones, such as Jade, Amber, Turquoise and Coral.
Traditionally, they are worn as necklaces and serve as a talisman of protection.
They usually conceal a paper made and blessed by a Lama to address specific life themes, such as health, happiness, prosperity, protection and attraction; also mantras, images, small Buddha figures.​

Amulets have been used in Tibet and Nepal for thousands of years, and have long been appreciated for their power and effectiveness.
Pilgrims carry large Gau boxes when they travel long distances: they carry them as a pouch or attach them to a belt around the waist as real travelling altars. They may have amulets, images or a statue of Buddha inside.
Depending on the instructions for each amulet, meticulously drawn and printed sacred patterns such as a yantra or mandala can be found inside. They used to be printed from woodblock prints on thin paper.

The impressions may contain mantras and seed-syllables (Bhija-mantras) of the deity to whom the person does his or her practice, but may also contain something else in general, such as the mantra of a protector deity.
Sometimes they are imprinted or painted with rare or precious substances that have an auspicious connection to the intended purpose. They may also be consecrated by coating them with saffron water containing relics and sacred substances.