A form of powered conveyor used to transport heavy unit loads such as pallets and industrial containers. These conveyors can be single or double chain strand in configuration. This chain is not only the driving force but it is also the part which comes in direct contact with the load and provides friction which pulls the load forward. In some cases, free rollers on either side of or between the chain provide additional support to the load. Short sections of double strand chain conveyors are a common means of transferring loads at right angle to/from another straight section of roller conveyor.