Measure the space you have to work with, including the height of your ceiling. Ideally, the space you are working with has a concrete floor. If not, a surface of, or similar to, stretched polypropylene works as well.
Outline the location of your two main posts, which should be nine feet apart. Using the cement mixture, secure the two posts in these locations either into or onto the flooring.
Attach the ends of the nylon net to the two posts. Do not stretch the net too tightly. It needs to have some give so the balls will not rebound when hit into the net. If the two posts run from the floor to the ceiling, attach the net to the ceiling between the two posts. If you have no ceiling to work with, string rope between the two posts and attach the net to this.
Run the PVC piping through the netting so the pipe sits equidistant between the two posts, suspended horizontally. Support this piping by attaching a rope to both ends and running these ropes to a location on the ceiling roughly four feet behind the two posts. This should cause the PVC piping to sit about two to three feet behind the main framework of the batting cage, determining the shape of the cage. If this is not the case, adjust the location of the ropes' connection to the ceiling.
Fasten the three 2-by-4s to the floor, using screws, ensuring that they sit fully on top of the net. The boards should be placed according to the natural shape of the cage. Make sure to leave at least a foot of slack for the net, to make sure the balls do not rebound when hit into the netting.