Entry hall 425 was an ancient water gate-control chamber, forty arm-lengths wide and fifty arm-lengths deep, situated directly above the main drainage junction of the Fourth Sector.
The floor was laid with massive slabs of dark olivine dark rock, sloping gently toward a central drainage trough two arm-lengths wide that ran straight down the middle of the room. Overhead, suspended from heavy bronze brackets anchored into the ceiling vault, hung a massive slab of hard black rock dark rock twelve feet wide and eight inches thick. An emergency solitude water gate designed to drop vertically and seal the hall in the event of an outer hull breach.
The slab weighed over eight thousand pounds, held suspended thirty feet above the floor by a single forged bronze release dog connected to an ancient balance weight arm in the eastern wall.
Qiao Ming stood beneath the suspended monolith, his bare feet planted wide upon the dark rock flags, his oilskin coat tied tightly around his waist to give his arms free movement.
In his hands, he held his ox-bone reel of horsehair line. He was tying a complex, five-fold knot around the tripping trigger of the bronze release dog. A knot designed to slip and release the balance weight when subjected to a sharp, level pull of exactly four pounds of tension.
