Rock Rosin Pound BagHave you ever wondered where rosin comes from, well we were wondering too so we looked it up. Rosin is a hardened tree sap that is generally used to make friction between slippery surfaces. In the dance world, rosin is used in a powdered or crystalline form (kind of like rock salt). Dancers apply rosin dust to their shoes (and sometimes their feet) to keep from slipping on a slick floor. The best way to use the Rock Rosin is to put some in an old sock