Acoustic line

I examined the metal key ring anchored to my vinyl runner. The morning draft from the door seam produced a low, faint vibration across the line. To monitor shifts without leaving my post, I needed an audible indicator. Near the wooden foot of the shoe rack, I retrieved a discarded hollow metal eyelet from an old bootlace. I carefully slipped the small metal ring over the taut vinyl strap, letting it rest just above the key ring's curve. With every sudden surge of air under the front door, the brass collar now chinks faintly against the steel coil. Early warning system operational.