Screw conveyors are used to transport materials along a plane. Screw conveyors consist of a helical screw element that rotates around a central shaft, driving the work material according to the screw design and rotational direction. The helical screw functions within a casing, trough or compartment in order to take full advantage of the rotational force. Roller conveyors are generally used to transport long items like wood battens, and panels. Material is moved along a series of driven rollers. Roller conveyors normally use parallel shaft or in-line gearboxes installed between a driven roller shaft and an electric motor.