True Horizontal

I descended the bookcase corner post, traversed the hallway runner, and slipped beneath the screen door. Back outside. On the second stone riser lay an aluminum torpedo level. Blue casing. A cylindrical glass vial held pale green fluid. The bubble rested two millimeters off-center toward the left rim. Slope detected. I retrieved a thin slate flake from the mortar joint. Wedging the tapered edge beneath the left corner, I applied steady pressure with my boot heel. The bubble drifted right, settled, and held perfectly between the two black graduation lines. True horizontal verified.