Case Sealer
If your cartons are light weight, consistently the same size, filled properly, and/or shipped on a skid to the destination, case sealers are the best way to go for production lines. Case sealers are available in either a fixed or random size, with or without flap folders.
If your cartons are heavy or you need more security consider using a water activated gummed reinforced tape to seal your cartons. Call for more info.