Build a basic grapevine trellis by stringing a series of heavy gauge wires at incremental points between two posts that have been anchored into the ground. The scope of the cultivation is a determining factor as to how large or strong the trellis must be.
Begin by anchoring an end post, which can be made of metal, wood or plastic, into the ground at a slight angle away from the trellis. Repeat this step with the second end post, angling it at an opposing angle at least 21 feet and no more than 30 feet from the first post. Using a 10- to 12.5-gauge wire, create horizontal supports that stretch from post to post and range from 30 inches to 6 feet from the ground. Attach these wires using affixing hardware appropriate to the end post.
GrapeGrowingGuide.com suggests anchoring the end posts to the ground using a ground stake or tie-back post, which can help support the structure while allowing the option of increasing the tension of the trellis. Install vertical line posts at various points between the end posts to give additional support to the vines.
SFGate.com advises planting no more than four plants in a 30-foot span of trellis. Grapevine naturally climbs, but growers often help train the vines onto the horizontal supports using an additional system of catch wires.