Size of tractor is 6 ft by 6 ft.

Front door.

Flipping down the door would act as a ramp for the chickens to come out.  Notice that I spray paint all hinges with metal paint to minimize rust issue.

Rather than using milk crates as suggested by Justin, I decide to build a rolling nest box for better egg gathering. 

The step in front of the nest box can also be flipped upwards at night to prevent the layers poop in side the nest box.

This is the back where eggs will be rolling out.  I use 1″ x 2″ hardware cloth as the bottom of the nest box with a layer of artificial turf on top later. 

We paint any wood exposed externally with wood stain.

Mounting the nest box on the back wall of the tractor. 

It just happened that I have lots of vinyl sidings around so time to get to work.

I am using leftover metal roof panel from other projects while I have to purchase a new PVC roof panel. 

The mobile chicken tractor is finished!  Notice that I have put a cover for the rolling nest box.  I did not use 2 big wheels as suggested in Justin’s plan, instead I used 4 small tires(for wheelbarrow 4.1 x 3.5 4-ply).  This would allow me to push or pull the tractor backward or forward easier than 2 wheels.