Crouching on the eastern seam in the late-afternoon sun, Kezra Venn examined the handiwork of workers who had lived and died hundreds of years before her mother was born.
The class rules in her bonded notebook were exactly rigid. Two exchanging parcels had to match their outer edge elevations within a single handspan along all four north-lined up edges after upright translation of their base planes. That rule protected the world from total shear disasters—preventing a map maker from dropping a thousand-foot cliff onto a flat meadow.
Here on the Knife Ridge, the ancient Reach-scale exchange had satisfied the law. The pale limestone shelf met the native dark rock crest with an upright mismatch of barely three and a half inches.
To a land-mapper looking down from an office balcony, three and a half inches was a triumph of care. But to a mule carrying three hundredweight of freight, or a traveler walking a narrow ridge in a mountain fog, a four-inch upright stone step with a foot-wide three-sided notch between two fractured rock faces was a total hazard. A boot caught in that crack would break a shin bone. An iron horseshoe slipping on that unmortared lip would fling an animal into the southern gorge.
