String beans grow on climbing vines that you will need to keep from touching the ground. Keeping string beans off the ground requires a trellis or structure that encourages the beans to grow upwards. Making a trellis for climbing string beans is not difficult. With simple lightweight lumber and some basic items, creating a single-sided or two-sided trellis should only take an hour or two. Because string beans and bean plants are not particularly heavy, you don't need to use excessively strong materials for this project.
Dig two holes 3 to 4 feet apart. The holes should be 6 to 8 inches in diameter and about 2 feet deep. Spacing and hole size is not critical.
Place a 6 to 8 foot long 1x1 in each hole, and lean them over until the tops touch. Tie the tops together tightly with string or rope.
Fill the holes supporting the poles. Pack the dirt tightly to keep the poles stable.
Continue down the row of beans, placing supports every 5 to 6 feet.
Staple netting to the poles to give the beans a good climbing surface. Consider planting a row of bean plants on either side of the trellis and covering both sides of the poles with netting.
If you don't have netting, staple wire horizontally between the poles. Space the wires every 6 to 8 inches to encourage the beans to climb upward. Direct any stray runners up to the next wire as the bean plants grow.