Damaru is generally made of wood in hourglass shape. In Chakrasamvara practices, the damaru is the prjna, to whom/which the male applies his skillful means (upaya) activating their union; the sound produced by drum is both the physical sound of the union and the mantras of the union. It is the sound of Great Bliss (Mahasukha) achieved, and depending on what a practitioner has been taught by a individual teacher, he or she may try to sustain the sound for prolonged periods of time. In theory, the damaru is made of the crania of adolescent youths, one male and female, thus the male-female nonduality is inherent even in the structure of the drum. In reality, however, virtually any skulls from the charnel fields will do.
Thus conceptually the damaru is made of two human skulls and connected at the point of the crown, at the hole of Brahma(brahma randhra), the imagined opening for the central meditative channel of the subtle body. In constructing a damaru, a hole is cut so that the two chambers of the drum are connected. The join, usually a pitch-based binder, is usually surrounded by a brocade band to which are attached cowries, a brocade handle, a tassel and embroidered silk banner or scarf. Two pouch strikers, the 'pellets' are strung from the waist of the drum. They generally hang from strings, so that when the drum is rotated rapidly, the weighted pouches swing around and hit the centre of the stretched hide. A decorative embroidered banner hangs at the centre of the drum and is often held alongside the handle, giving the yogin a good grip on the drum. He or she will hold it aloft with the right hand and, rotating the forearm and hand, produce a rapid continuous beat. In the hands of practice meditators, the modulations from very soft to quite loud, and from a slow, rhythmic resonance to very rapid staccato beats almost blend into a single tone.
In Tantric visualizations, the sonic symbology of the bell and damaru are extremely important in the process of purification of both the external and the subtle body. These instruments signify the radiant bliss of realized wisdom, specifically when the bell is held in the left hand and played at the level of the heart. It symbolizes the experience of clear luminescence (prabhasvara) that arises through the purification of the inner body. To attain the realization of the clear light, the inner fire of Vajravarahi at the navel must be ignited and increased as it moves upwards, awakening the subsequent chakras. In the completion-stage meditations of Vajravarahi, this moment is symbolized by holding the vajra and damaru with the right hand. The drum is played near the navel chakra to awaken Vajravarahi, the personifications of the inner fire, to initiate the experience of clear light. This is then accompanied by the ringing of the bell held in the left hand and placed in the proximity of the heart chakra, signifying the actual experiencing of the radiant light of bliss through the purification of the subtle body. In this may, the sonic energy of the bell and damaru mark the culminating moments of the completion stage, specifically associated with the Yogini and his or her purifying heat, in this case, Vajravarahi.
Thus, Damaru has a very important place both in Brahmanical and Buddhist rituals.