The corridor opened onto a recessed concrete dock. A corrugated steel bay door sealed the brick wall, anchored by an endless loop of galvanized hoist chain dangling against the jamb. I moved in. Cold zinc, thick links welded true. I planted my boots on the diamond-plate steel sill and grabbed both sides of the vertical run. Two sharp pulls downward. Above, the heavy geared drive clanged, pawls biting hard into cast-iron teeth before settling under counterweight. No give. The bay remains barred. A formidable threshold.