The most common way to build tomato cages is to use either a chicken wire fence or concrete reinforcing wire. You can find either of these with a mesh that’s large enough to put your hand through, which will allow easy harvesting of the tomatoes when the time comes. The fencing is looped back on itself in a way that forms a large tube, best build a backyard greenhouse which is set over the tomato plant and it grows up inside the cage. With this approach there is not as much need to tie up and prune the plant, the plants will just climb through the holes and naturally support themselves.