Please post photos and details of your wire grid trellises here! The photo shows ordinary green garden grid, which you can easily find at Home Depot, Lowes or your local garden center, attached to a fence. This is a low-cost choice that is less visible than a traditional trellis once the vines are growing. They work very well with combination plantings of roses and clematis, and the roses canes can completely mask the underlying grid during the dormant season. In this area, I used clay chimney flue liners to hold the clematis high to avoid drainage issues. The wire it attached to the fence with galvanized L-brackets. I'll post a new picture this spring when the vines are covering the fence.
Some gardeners use fishing line or heavy rolled wire strung between eye hooks for this purpose as well.
Wire grid can be used as a support to start clematis around trees or to lead a clematis toward another structure or plant. It can be used other items to encourage the clematis to "smother" something you find unsightly. There are so many uses for this. Please, share your ideas!