Decide the type of vegetables you want to grow to determine the type of trellis you should make. For light vegetables like peas or lima beans you can make a trellis with posts and chicken wire or mesh netting in-between. Heavier vegetables, however, need heavily constructed trellises.
Place two 8-foot long lumber 2-by-4s vertically on a clean floor, spacing them 5 ½ feet apart.
Measure 24 inches from the ends of both the 8-foot lengths with a measuring tape and mark the exact location with a masking tape or marker. This bit will be underground to hold the trellis firmly up.
Lay a 6-foot lumber 2-by-4 horizontally on the top ends of the vertical posts. Lay the other 6-foot lumber horizontally over the bottom ends of the posts, 1 inch over the marks.
Wear your safety glasses and earplugs and attach the four corners of the framework with a drilling machine and galvanized deck screws. You will now have a large square framework with two 24-inch legs.
Take a measuring tape and measure 36 inches on the top horizontal length of lumber. Mark the spot with masking tape. Measure and mark 36 inches on the lower length as well.
Lay a 6-foot 1-by-2 board directly over the top and bottom marks and attach it to boards below with galvanized screws. You will now have a frame with a vertical length of wood running straight down the middle.
Measure 1 foot down from the top of the frame and mark it on both vertical sides. Space the other four boards 12 inches apart in the same vertical manner.
Lay a 6-foot 1-by-2 board over the marks and drill it in place with galvanized screws. Repeat with all four boards.
Use a shovel or post hole digger to dig two holes in the ground that are 1 ½ feet deep. Fill 6 inches of gravel in the hole to hold the trellis in place, and prevent it from shifting when the soil is wet.
Insert the trellis into the holes and tamp it down with a stick to fill and gaps or holes. You can build several trellises like this for growing different vegetables, altering the measurements to fit your garden space.