A baler is a machine used to compact and bind corrugated cardboard, paper, plastics, and aluminum into bales for recycling. The machine term is a recycling baler. A recycling baler is a used to compress and bind a volume of corrugated cardboard, paper plastics, and aluminum. Depending on the baler used, recyclables would generally be baled into a round or rectangular shape for easy stacking, transportation and storage.