Almost all U.S. LTL carriers use NMFC freight classes, although some are attempting to move to a dimensionally-based system.
Working with a 3PL like Koho can help you accurately determine your freight class so you can avoid re-classification fees with the carriers. For more information on the freight class system, go to the National Motor Freight and Traffic Association.
Yes. If your shipment can be stacked, it allows the carrier to fit more freight into their truck.