Pendulum Calibration

A brass plumb bob hung from a length of coarse twine looped over a high nail above the workbench, its tapered tip hovering two inches over the blue chalk line I drew this morning. Its sway was erratic, driven by cross-drafts. I grounded my stance along the rough timber grain, unsheathing my blade with a steady two-handed grip. Aligning the flat of the steel parallel to the line, I caught the spinning brass point gently on the blade's surface, halting the irregular wobble. Lowering the tip downward in a single plumb descent, I released it. The brass bob began a pristine, silent pendulum arc, its point slicing back and forth directly along the chalk coordinate without deviating a hair.