rosin

A sticky, ground powdered substance made from tree sap, and used by dancers, especially in ballet to gain traction and counteract a slippery floor. Often a company will have a "rosin box" (called "litter boxes" or "cat boxes" by the crew) on each side of the stage. This is nothing more than a tray about 2" deep, and large enough so that a dancer can place one foot in to accumulate rosin and shake off the excess.