Aperture Calibration

I advanced along the concrete pavement toward a heavy red cast-iron post box at the street corner. Its spring-loaded horizontal deposit flap was seized three centimeters ajar, wedged by an unyielding plastic-coated parcel envelope left halfway in the entry slot. Such partial occlusion compromises mechanical enclosure. I mounted the raised granite curb, braced my stabilizers against the curved iron casing, and took hold of the stiff cardboard edge with both hands. Applying sustained inward pressure through my shoulder joints, I drove the obstacle through the internal throat. The parcel dropped with a hollow interior thud. The steel flap snapped shut against its recessed lip with a crisp, definitive clang. Perimeter integrity is sealed.