The thavil consists of a cylindrical shell hollowed out of a solid block of jackfruit wood. Layers of animal skin (water buffalo on the right, goat on the left) are stretched across the two sides of the shell using hemp hoops attached to the shell. The right face of the instrument has a larger diameter than the left side, and the right drum head is stretched very tightly, while the left drum head is kept loose to allow pitch bending. The larger face is higher in pitch than the smaller face.
The instrument is either played while sitting, or hung by a cloth strap (called nadai) from the shoulder of the player. The right head is played with the right hand, wrist and fingers. The player usually wears thumb caps on all the fingers of the right hand, made of hardened glue from maida flour. The left head is played with a short, thick stick made from the wood of the portia tree. It is not uncommon for left-handed players to use the opposite hands, and some nadaswaram groups feature both a right- and a left-handed thavil player.