I built a chicken tractor and it was super easy. I took used 1x1 and made 2 frames at 10'x4'. Inside each of those frames I measured 2' from the end and added a 1x1 brace. I used 1x1 vertically at each corner to connect the frames and 1x1 to connect the braces. I made it 2' tall. I took a sheet of plywood and sawed it in half lengthwise. Take one of the halves and saw it in half so that you have 2 sections measuring 2'x4'. The small 2' section of your frame (between the braces and the end) is going to be the shelter. On a the end wall where your shelter is, you will nail on of the pieces of plywood. Hinge the other piece to the top. Cut two 2' sections from your final piece of plywood for the sides. You will have an extra 4'x2' section left. This will be a removable piece that you just lay on top for additional protection when/if needed. Now, take chicken wire and staple it to the other end of the tractor, fully enclosing it. Don't forget to make it so you can pull that back if necessary (I made that mistake). You can put handles on each end and move it around.
Total time to make it...1/2 day. I woke up one morning and decided I was going to have chickens, drew up the plans really quick, drove to town and picked up the materials, came home and built it. I did have help stapling the wire on.