This is how I make a trellis for my beans and peas. I pound 2x2 or larger posts into the soil about 5 feet apart. I then take a batten slat or any 1x1 or narrower and nail it to the bottom of each post about 5 inches from the soil line. Nail another at the top of the post. Drive small nails into both slats, about 6 inches apart and leave 1/2 of nail exposed. Put these small nails in before you attach the slat to the post. Using good quality twine, [butcher string works good] weave top to bottom along the length. Instead of nails, small hooks would work well. Take it apart in the fall and you're set to reassemble in the spring. Just set the post and attach the slats.

This is my first year doing pole beans. I have found on this post photos of a cattle panel hooked on each end and bent to make an arch.. I just bought one and plan to the the same with mine. Do a search and you will find that 20 bucks is a small investment.