Stretch #9- or #10-gauge galvanized wire between the end posts, 21/2'above ground level, and clamp it securely. Then staple it to the other posts. Add another trellis wire at the top of the posts, and one or two additional wires between them.
Hammer large nails into both sides of each post about halfway between each pair of trellis wires. These nails will support catch wires, used to lift the vines up to the permanent trellis wires during the season. To make catch wires, cut tow pieces of lighter-gauge wire that are as long as the full trellis. Connect short pieces of chain to each end of the catch wires. Hook the chains over the end post nail, and let the wire rest on all the other nails.
Grape shoots will climb permanent trellis wires on their own, or they can be tucked through by hand during the season. Movable catch wires go around the trellis like a giant rubber band and keep shoots pointing up. Drop the catch wires to the nails below the vine heads when you prune each winter. Once growth starts and shoots are about 2' long, raise the catch wire to the nails above the vine head; as you lift it, the wire will pick up any shoots that are straying from the trellis. Raise the wire to the next set of nails as the shoots grow, or use a second catch wire.