The center of the trellis will consist of various string supports attached to nails. To build the string supports, begin nailing 1 1/2" galvanized flathead nails to the inside of the boards. Space them about 10" apart. Leave about 1/4" of the nail sticking out, leaving space behind the head to attach the string (Image 1).
Use a ball of garden twine to create the netting on the trellis (Image 2). You can also use fishing line or plastic garden fencing to face your trellis. Begin at the bottom nail and tie off one end of the string. Pull the string across to the second board and looped it around the corresponding nail. Then go directly up to the next nail, loop the string around and then pull it back to the first board. Continue looping and pulling the string until the entire span of the trellis is laced. Tie the string securely to the last nail.
The final step is to install the vertical trellis strings. Start at the top by attaching the string to a nail. Drop the string straight down and tie it to a horizontal string with a single knot each time the strings cross (Image 3). At the bottom horizontal string tie off the string and then cut it off.