Grape vines need a supporting structure on which to grow. If the plant isn't supported, it can form a thick tangle of vines with poor quality fruit, climbing on anything that happens to be close by. You can construct a trellis with a few supplies and tools and keep your vines off the ground and under control.
Position your trellis in a north to south orientation. This way the grape vines will get the maximum sunlight as the sun rises in the east, passes overhead and then sets in the west. Make sure it is in an area with good drainage and full sunlight.
Measure out your trellis area so that each vine will be about 4 feet apart and the ends of the trellis are between 18 and 20 feet apart. Mark the ground at either end of your row. If you are planning several trellises, measure twice so that they run straight and are the parallel to each other.
Dig post holes for your end posts, the sturdy 6-by-6 timbers. If you set them into the ground at 30 to 36 inches deep, they will be strong enough to hold the weight of several grape vines. Set aside the soil that you remove from the hole.
Set the poles in place and hold them straight up and down. Use a level to make sure they are straight and then fill in the soil around them. Pack the dirt down hard, using the end of a 2-by-4 or a tamping tool, until you have filled the hole.
Drill holes straight through the end posts to feed the support wires through. Use a large 1/2 inch drill bit that is at least 8 inches long to be able to get through the post. Plan to string the wire every 18 inches, measuring from the ground up. If you are planting on a slope, use a level to determine the position for the holes to compensate for the pitch.
Thread the wire through the holes, wrap around the pole, and then twist it back on itself, keeping it tight as you go. You should have at least three strands of wire for each trellis. You can now tie off your grape vines to the trellis.