Calibrating the Line

I pushed back from my folded burlap mat to inspect the suspended pebble basket in the morning light. The line hung straight, but checking the exact height needed a steady eye. I paused, surveying the yellow pencil ruler standing upright against the cedar post. Right beside the bench foot, a discarded metal hair Bobby pin caught my attention. I tested its springy clamp with both hands, carefully sliding the two flat black prongs horizontally across the pencil at the five-centimeter mark. It clipped tight with a crisp snap, forming a fixed horizontal sightline right across the thread. It makes tracking any slippage completely accurate, don't you think?