One of the very best tips I ever got out of “Square Foot Gardening” was for making plant protection cages. Several years ago I bought a roll of 1-foot wide powder-coated wire garden fencing, and cut it up to make cages.
I cut it into strips that were 3 feet long, plus the width of one extra mesh square on each side. By staggering the cuts of the wire at each end, you get prongs at each side that are used to insert the ends into the ground.
Then you just fold the wire so that you have a cage with three 1-foot sides (plus the prongs to go into the ground).
If you want mesh on all sides, just stack one crosswise over the other – helpful if you want to keep birds or other critters away from the plants.
You can cover them with cheesecloth or shade cloth to protect new transplants from the sun,
or cover them with plastic to protect tender plants from cold or frost, or to help newly-sown seeds germinate. You can even cover them with fine screening to keep out birds or insects.
And they make good grow-through plant supports. Hey, look – I have peas coming up!
At the end of the season, just bend them flat again for storage.
Of course, you could also use chicken wire or other types of mesh fencing material. I liked this kind because it blends in well in the garden.