Each net was square, about half the size of a football field. It was suspended at each of its four corners from a steel pole that projected to a height of maybe fifty feet from a concrete footing in the ground. The setup couldn’t have been much simpler: At the top of each pole was a pulley with a steel cable running over it. One end of that cable was carabinered to a corner of the net. The other end ran down the pole to ground level where it disappeared into a winch. When all four cables were winched tight, the net stretched overhead like a roof, sagging a bit in the middle, but nowhere less than about thirty feet above the ground.