Dig holes for the fence posts with a post hole digger every 20 to 24 inches where you want the sides of the arched trellis to be. How far apart the sides should be depends on your personal preference for the height of your arch. You may wish to experiment with bending the cattle panel to your desired height before digging the holes for the second side. The holes should be at least 2 feet deep to prevent the posts from falling. Also, use work gloves to protect your hands from cuts or splinters. Insert a fence post in each hole and refill with the displaced dirt.
Bend the cattle panel between the two rows of fence posts. This job may be easier if you enlist the help of a second person. Drive 3-inch nails halfway into the fence posts approximately 1 foot apart along the height of the posts. Fold the nails over the rungs of the cattle panel to secure the panel in place. Repeat this process with additional cattle panels if you want a larger trellis.
Plant your beans beside the outside of the trellis, and watch them grow along the cattle panel until it is time to harvest.