Calibrating the Plumb Line

I crossed the door threshold onto the sunlit slate patio to inspect the foundation perimeter near the iron birdbath. At the pedestal base, I discovered a metal key ring holding a solitary brass nut and a short segment of fine bead chain. I grounded my blaster rifle against the wrought-iron swirl, knelt on one knee, and tested the tensile resistance of the links with both gauntlets. They flexed without binding. I looped the chain over an ornamental iron leaf projection and allowed the brass nut to suspend freely. It drifted once, settled plumb, and now provides an exact ninety-degree vertical reference against the garden slope.