The vajra is believed to represent firmness of spirit and spiritual power. It is a ritual tool or spiritual implement which is symbolically used by Buddhism, Jainism and Hinduism, all of which are traditions of Dharma. Because of its symbolic importance, the vajra spread along with Indian religion and culture to other parts of Asia. In Tibet it is called dorje.
In Tantric Buddhism the vajra and ghanta (bell) are used in many rites by lama. The dorje is a male polysemic symbol that represents many things for the tantrika. The vajra is representative of upaya whereas its companion tool, the bell which is a female symbol, denotes prajna. Some deities are shown holding each the vajra and bell in separate hands, symbolizing the union of the forces of wisdom and compassion, respectively. These Buddhas are in Gyantse and reknown for how lovely they are. Standing some 5m, it is a pretty powerful site.