(Monkey Wrench, OH-36-20) SW of Greenfield, Madison Township, Highland County, OH. OH138 SW 1.65 miles from jct with OH753 in Greenfield to the quilt on the SE side of the road at 11530. John & Wendy Royse. (N39 19.698 W83 24.641) Photos by Jack & June Schmidt 7-16-15.