Place a large growing stake or wooden stake at all four corners of the tomato plant. For multiple plants close together, place a stake at each corner of the batch of plants. Place one stake in the center of a group of plants, as well.
Lay a large plastic sheet, tarp, or old bed sheet over the tomato plants. It should rest on the tops of the stakes. It can touch the plants, but should not lie on the plants for weight support, as this can damage the leaves and stems.
Smooth out the excess sheet or tarp on the ground around the plants so it is flat on the dirt. Place rocks or bricks on top of the excess tarp or sheet where it meets the dirt. This will help prevent the sheet or tarp from blowing around.
Remove the cover, or lift it up enough during the day, to allow sunlight and water to reach the plants. Re-cover as the cold night approaches.