Unroll a coil of 4-foot-wide rebar with 6-inch squares, wide enough to get your hand through to harvest tomatoes. Measure and mark the rebar at 60 inches.
Cut the rebar with a bolt cutter or angle grinder one wire at a time, either flush to a vertical wire to fasten it with ties or halfway between two vertical wires to hook the rebar to itself.
Pull the cut rebar into a round shape. Wire the cut edges together with rebar tie wire or cable ties, or form hooks by bending the cut wires with pliers.
Cut off the bottom reinforcing wire to create spikes that you can push into the soil.
Place a cage over each tomato plant at the time of transplanting. Secure the cage with stakes on opposite sides of the cage.