Garden peas need support to keep them off the ground where they could rot. The solution is to build a trellis of two vertical posts with a horizontal piece connecting them at the top. You'll then use twine both vertically and horizontally between the support posts. The result is a grid of twine for the tendrils of pea plants to cling to as they grow.
Build the Frame
Measure the length of the area where you want to plant your peas. Plant climbing peas about two inches apart in the row, with the rows about three feet apart.
Purchase a sufficient number of six- or eight-foot-long one-inch-by-two-inch boards to reach the length of the row(s) you are planting. Include in your board purchase one-inch-by-two-inch boards as vertical supports every four to six feet. You can use metal or polyvinylchloride (PVC) pipe instead of wood. You can also purchase pressure-treated wood, so it won't rot like pine boards will over time.
Purchase a large spool of heavy-duty twine and screw-in eye hooks to be spaced every six inches on the interior side of both the vertical and horizontal boards. Instead of eye hooks, you can drill holes at six-inch intervals and thread the twine through the drilled holes.
Pound two upright one-inch-by-two-inch boards 18 to 24 inches into the ground at opposite end of your row of peas. Cut one end of the board at a 45-degree angle to create a point that may help the board to penetrate the ground. Cut a board to fit across the top of the two uprights and nail or screw the horizontal board to the two vertical uprights. The frame of your trellis is now in place.
Pre-drill holes starting about four inches off the ground and at six-inch intervals on the inside of the trellis frame and then insert the eye hooks. The pre-drilled holes should be slightly smaller than the screw end of the eye hooks. Another option instead of using eye hooks is to drill holes at six-inch intervals that go completely through the frame. Make the diameter of those holes wider than the diameter of your twine to help weave it through the hole.
Add the Twine
Run the twine through the first hole or eye at the bottom of the frame and stretch it across to the opposite bottom of the frame. Run the twine through the opposite eye or hole and then upward to the next eye or hole and back to the first post. Pull the twine so it is taut. To help keep the twine evenly taut across the whole trellis, knot off one side at every other row. You don't have to cut the twine. Repeat the process of running horizontal twine and knotting off every other row until you have reached the top of the upright posts.
Cut a strip of twine about two feet longer than the height of trellis frame. Knot the cut strip at the first eye or hole on the top board. Drop the line straight down and where it hits the top horizontal line, tie a loose knot like when you tie your shoe strings just before making a bow. Drop the twine down to the next horizontal line and again, tie a loose knot. Continue down, tying a knot at each horizontal line. When you reach the bottom row, tie a square knot or other sturdy knot.
Continue the process of cutting a length of twine. Knot it at the top of the frame and at each horizontal line straight down, until all the eyes or holes of the top of the frame are connected to a line dropped vertically.