A duct rodder is a long, flexible rod, typically made of fiberglass, that is wound on a reel. Its main function is to feed a pulling line or a rope through a conduit that is already in place. The rodder's stiffness allows it to be pushed over long distances and around bends without bunching up. Once the rodder reaches the other end of the conduit, the pulling line is attached to it, and the rodder is reeled back, pulling the line through.