Before planting, make a scale drawing of your design on paper so that you can space trees properly and refer back to your plan at pruning time. A sketch will also help you decide how to realize your design—with a wood- lattice frame or a grid of wires for support, perhaps—which will dictate the construction materials you need. If you're working with a wall and hope to capture extra warmth for fruit, pick one that faces south or east.
Shown: On a backyard patio, a planter box with a trellis is an accessible setup for training an espaliered tree. Simply tie the plant's branches directly to the wood slats as they grow and spread, using jute twine or some other soft, flexible type of plant tie.