Scaler needles are metal rods that needle scalers rapidly and repeatedly strike against surfaces to clean off coatings and buildup. They are commonly used to remove rust, paint, dirt, and welding slag from metal surfaces. The needles are held in a loose bundle in the scaler's barrel, so they move independently to follow curves and contours. These needles are used with a compatible scaler to replace broken or worn needles or to change to a different needle diameter or material.