Martha first detailed this technique in her blog here, and again here. Below is a picture of her espalier apple orchard at her Bedford farm.
Recently, she got another espalier orchard with a different variety of apple. The trees were bought already with the espalier form. Isn't that amazing?
One day, I'd like an espalier orchard of apples, pears and peaches in my backyard. I'll have to speak with my gardener about that.
NOTE: pictures are from Martha's blog. Follow the links to see more. :)