This year I am trellising my tomatoes. I planted the seedlings very deep, then added 1-2 inch collars (for cutworm protection).
The trellis stem is made up of two upright posts set into the ground 6 feet apart. Each post has a hole at the top. Through the two holes, I thread an 8 foot metal pole.
Twine provides the support for the tomato plants. To set up the twine, I cut a length twice the height of the pole from the ground and laid this over the metal pole with the middle of the twine resting on the pole. I then tied a knot next to the pole to hold the twine in place.
For now, I have loosely wrapped the ends of the twine around the little plants. When they are bigger, I’ll tie the twine loosely to the stem of the plants. As the vines grow, I’ll wrap the twine around the stem of the plant so that it stays upright and off the ground. I’ll also trim off any suckers so I get a tall straight plant with lots of room for airflow.