Gravity Roller and Skatewheel Conveyor is used for any number of tasks, if you look at the automated sortation picture, all the lanes are done with gravity.

Gravity Roller and Skatewheel Conveyor can be used as a working pick transport, ie.. put gravity directly in front of a main powered conveyor, and you can use it to roll a carton on as you fill it, when done just slide it off onto the powered conveyor for transport to its final destination.