Acoustic Return

I completed my descent to the ground floor vestibule as darkness settled. Near the bank of rowed iron mailboxes, a discarded flat metal key ring lay beside an unbent steel paperclip. I paused to gauge the surface tension. Planting both feet squarely against the cold ceramic floor tiles, I wedged the tip of my red blade beneath the split edge of the ring to pry the coil open slightly. With measured precision, I threaded the straight arm of the paperclip between the twin steel loops until it locked into an upright post. A deliberate tap with my hand sent a sharp, clear ping echoing softly against the metal lockers. Resonance verified. Ground outpost secure for the night.