Setup the ridgeline. Attach 2' lengths of chord to middle grommets on the a frame with half hitches. secure these to the ridge line w/ taught-line-hitches (magnus hitch) leaving the standing end dangling. The magnus hitch only slides one-way on the ridgeline, allowing you to stretch the tarp taught. This configuration eliminates any sag in the ridge, as well as allows a drip line at each end. Go to UTUBE and search for "rigging a tarp" for a video by ray mears showing a good way to secure the ridge line tighly to the trees for easy removal. The great thing about this technique is that the tarp will be taught even if the ridge line is somewhat loose.