Truck Transmission Loses Reverse, Owner Devises Way to Make It Go Backwards Anyway

The rollers (the narrow white tubes) reverse the direction in which the rear wheels push on the ground. Imagine a pair of two gears meshed together or rubber wheels. If one gear turns clockwise, the other must turn counterclockwise. The truck's rear wheels are like the driving gear in this case, and the rollers act like the other gear. The tire turns "clockwise", and the roller "counterclockwise", just like putting the vehicle in reverse (the front wheels can spin freely in either direction). The chains serve as axles for the rollers, keeping them in place under the wheels. Makes sense?

Yes. What he said ^
The tires no longer touch the ground. Instead by going forward the tires drive the cylinders in reverse and the reversing cylinders are in contact with the ground.

Quite brilliant. My old Pinto had no reverse for a while; I had to be really careful where I parked.

Ingeniously simple yet still needlessly elaborate - In most situations I'd just get out and push :)