To make a cage about 2 1/2 feet wide, cut an 8-foot long piece of wire mesh such as chicken wire or concrete reinforcement wire or have the hardware store cut it for you. Depending on the type of tomato you are planting, the mesh should be between 5- and 8-feet tall. Use wire cutters to cut away two rows of horizontal wire and one vertical row on one long side to create spikes to stick the tower into the soil. After rolling the wire into a cylinder, secure the edges by crimping the wire together. Shove the spikes into the dirt at a slight angle to stabilize the tower. As the plant grows, direct the vines through the holes in the mesh wiring. To help the plants remain upright during early growth, place a wood stake into the dirt in the middle of the tower.
Cut four stakes with widths of 1 to 2 inches into 4- to 5-foot pieces. Place them into the ground evenly spaced to form a circle or square around the tomato plant. Wrapping twine or thin wire around the outside of the stakes will create several rows of support for the vines as they grow. For added stability, wrap the twine or wire around each stake several times before proceeding to the next.
In the plumbing section of a hardware or home improvement store, purchase 1/2-inch connecting conduit in various lengths. The conduit can be PVC, copper, or another metal. The vertical supports need to be at least 5-feet long and the horizontal conduit around 3-feet long. You'll need to purchase enough double-sided connectors to screw the pieces together. Screw the sections together until you have four identical walls, and then attach the walls together with connectors. The structure will be a bit wobbly but will become steady when the legs of the cage are shoved into the dirt. As the tomato plants grow, thread the vines in and out through the open walls of the cage. If the plant starts to outgrow the cage, add more sections of conduit to increase the height.
Small tomato varieties such as cherry or grape that grow in bunches tend to be taller than standard varieties, so they may need taller towers and extra support in the form of stakes or ties. You can tie the vines to the sides of the tower or to a center stake with wire garden ties, string or thin strips of cotton or old pantyhose.