[header] How to construct an inexpensive shelter [title] Build two parallel four foot fences, thirty feet long. [step] They need to have a distance of 13' 6 " between the outside of the walls. In addition, make sure that they are exactly opposite each other so if there was an enclosure between each end, it would form a perfect rectangle. 
This means that the distance between diagonal opposite ends should be the same (32'11 "). [title] Find the four end posts that will create the imaginary rectangle.