A rainstick is a long, hollow tube made from bamboo or dried cactus. It is partially filled with small pebbles, rice, dried beans, or other hard granular materials. The inside surface of the tube has small pins or thorns arranged in a spiral pattern. When the stick is rotated and held upright, the pebbles fall to the other end of the tube, bouncing off the inside bumps or spikes to create a sound similar to falling rain.

In South America, rainsticks are believed to have been invented by the Mapuche people. They were used in the belief that the instrument could bring rainstorms. Rainsticks were also found further north along the coasts of Chile, possibly used by the Incas as well. Mapuche rainsticks are usually made from several types of cactus, such as Eulychnia acida and Echinopsis pachanoi. The cacti, which are naturally hollow, are dried in the sun. Their spines are removed, and nails are driven into the cactus like screws. Pebbles or other small objects are placed inside the rainsticks, and the ends are sealed.

Variants of the instrument can also be found in Southeast Asia, Central Asia, Australia, and Africa. In these regions, rainsticks were developed independently and are often made using bamboo instead of dried cactus.

Rainsticks may also be made with common household materials, such as paper towel rolls instead of cactus, and nails or toothpicks instead of thorns. These versions are often sold to tourists visiting parts of Latin America and the Southwestern United States, which has a history of Spanish and Mexican cultural influence.