This hip trick is featured on page 168-9 of the book (in both print editions!) See what a fine job Agent Meredith did of illustrating?!

No matter your garden or plant scenario, you can create a quick and easy trellis from an existing deck or railing structure to train new growth and vines up. You need a bit of jute twine and a dowel or anything long and skinny and relatively light to form a ledge. Follow the method on page 168 of the book for tying the twine tightly around both the dowel and the railing or structure, or just wing it (seeing as there’s no one right way to do this)!