Great Lock

Where it stands

The structure holds 16 chests with loot, 6 kinds of contents; the chance is to find the item at least once per chest.

The pages the structure keeps in its rooms; the hints to its locks are among them.

Spoiler: this reveals part of the walkthrough.

The Reckoners led the main race straight through this chamber to measure it. Quays at the race; galleries and leaf halls in the walls; the lower head keeps the count.
The east door opens when the race thread reaches its gauge mark across the chamber. Then lift the water in the lock chamber to its mark.
Every rod keeps one level of the race. The tenders keep the rods. Nobody keeps the tenders now.
Count the beads that pass the gate in a breath; write the count; never trust one count.
The race in small: what turns here turns there. We tried every leaf on the model first.
A leaf along the thread lets it pass; a leaf across stops it; a leaf aslant turns it aside. Lead the thread to the gauge mark.
The thread must braid the whole hall before it reaches the mark. The tenders set the leaves back; be quicker than they are.
The leat comes down from the north wall and runs for the door. Turn it back around the posts to the west mark.
Raise the water to the lit mark of the pit, and the gate of the lower head rises. Upper wheel lets water in, lower lets it out.
The pit is full; the mark is low. Let it out, let it in, let it out again: count the spans on the wheels.
An empty basin; the mark is high. Alternate the wheels — one wheel alone never stops at the mark.
Here the Reckoners kept a record of every chapter and the hub of the Wheel they measured by.
Level, speed, current, hour — four columns, one line per bead count. The race never wrote the same line twice.