Fellis Dain sat on the edge of the wedging bench. That turned his duplicate advancement sheet over in his calloused hands.
He had spent his entire life working with box-shaped timber baulks, tube-shaped rope coils, and three-sided rigging bridles. His tradesman’s mind right away seized on the rigid sharp-angled symmetry of the progression table.
“Look at the dimensions, Kezra,” Fellis said, tapping the scale column with his thumbnail. “Every single rank is a square prism. Step is four by four paces. Plot is sixteen by sixteen. Reach is sixty-four by sixty-four. Quarter is two hundred and fifty-six by two hundred and fifty-six. Horizon is one thousand and twenty-four by one thousand and twenty-four. Why does every rank multiply its width by exactly four?”
Kezra pulled her brass dividers and folding ruler from her pocket. She set them on the cedar boards between them.
“Because the survey grid is based on quarter-width divisions,” Kezra explained, demonstrating with the dividers. “A four-pace Step square is divided into four one-pace quarters along each edge—sixteen inside cells. When the class expands to Plot scale, each of those four-pace cells becomes an entire Step prism. A Plot square is exactly sixteen Step squares joined together. A Reach square is sixteen Plot squares joined together. The shape nests like Maud’s clay pot trail-pots: four quarters along each axis, sixteen cells in every layer.”
“And the depth?” Fellis asked, pointing to the second number in each bracket. “Step depth is two paces. Plot depth is eight paces. Reach depth is thirty-two paces. Quarter depth is one hundred and twenty-eight paces. Horizon depth is five hundred and twelve paces. In every single rank, the depth into the earth is exactly half the surface width.”
“A one-to-two aspect ratio,” Yseld remarked, leaning back against the porch railing. “In mountain stonework, a retaining wall that holds back a hillside must have a foundation depth equal to half its upright face to prevent basal shear. The class mirrors the physical balance of stone.”
Kezra turned to the marginal rubric that had unlocked beside the Plot sign-off, reading the sharp-angled constraints aloud:
“Rule One: Fixed North Posture. Every surveyed prism must align true north to south and east to west along its boundary planes. No rotation is allowed. You can’t angle a square thirty degrees to fit a crooked road or match an angled fence.”
Fellis grimaced. “So if a road runs northeast along a ravine, you can’t lay your square parallel to the track? You have to orient the prism true north, even if the corners bite into the hillside?”
“True north only,” Kezra confirmed. “The bedrock deep ring couples with the magnetic orientation of the planet’s crust. If an anchor is cut even two degrees off true north, the sign-off refuses to form.”
“Rule Two: Zero Polygon Flexibility. All parcels must be equilateral square prisms. No rectangles, no triangles, no arbitrary polygons. You can’t trade width for depth. A Plot parcel is sixteen by sixteen by eight paces. You can’t make it eight by thirty-two by eight paces to fit a narrow street.”
“Rule Three: Smaller-Scale Retention,” Kezra continued, pointing to a crucial line of text. “Unlocking higher ranks doesn’t discard smaller scales. A Plot Mapmaker may survey and activate a four-pace Step exchange whenever a smaller transit is needed. A Reach Mapmaker may choose between Step, Plot, or Reach scales.”
“A vital tactical distinction,” Paxa noted from the table. “If you only need to swap a small wagon across a stream, you don’t want to move sixty-four paces of forest and suffer a three-day global lock. You use a Step or Plot swap, take the twenty-four-hour lock, and keep your options open.”
“Rule Four: The Whole-Structure Rule,” Kezra read. “Every attached building, retaining wall, stonework foundation, or living root system must sit wholly inside the boundary prism. If an exchange parcel contains a house, the entire foundation beam must lie within the square. If an attached porch or lean-to projects across the boundary, the exchange is blocked. Living bedrock and nonstop soil layers may end cleanly at the upright boundary plane, but man-made structures can’t be sliced.”
“Why?” Fellis asked. “Why can’t you slice a timber beam?”
“Because an intact building is a clockwork continuum under tension and squeezing,” Fellis answered himself. He nodded as he thought through the carpentry. “If you shear a load-bearing foundation beam at the outer edge seam, the leftover half of the roof truss has its king post torn away. The timbers would buckle instantly under dead load and collapse into the street. The class refuses to trigger a total load-bearing collapse.”
“And Rule Five: The One-Handspan Elevation Rule,” Fellis said, nodding in recognition. “The rule that stopped you on the west kiln slope two days ago.”
“The most unforgiving rule of all,” Kezra agreed. “When two parcels are paired for an exchange, their relative outer edge contours along all four edges must match within one handspan—less than four inches—after upright translation. You can swap flat ground with flat ground. Or a terraced shelf with a matching terraced shelf. But you can’t swap a thirty-degree hillside with a level pasture. The outer edge overhang would create a shear hazard that the class forbids.”
Fellis reached across the table, took four wooden wedging blocks from the potter’s scrap box. Then he arranged them in a neat square on the cedar boards.
“Let’s see the shape in physical timber,” Fellis said. He set a fifth, taller block of pine across the boundary seam between two of the square blocks. “Suppose this taller block is Maud’s glaze kiln. It’s built of firebrick, twelve feet long and eight feet wide. If Kezra surveys a four-pace Step square that cuts through the middle of the kiln—so that the firebox is inside the square and the chimney pipe is outside—what happens when the stone moves?”
“The class refuses to activate,” Kezra answered, tapping the fifth block. “Because the kiln’s brick arch forms a nonstop crushing structure. The bricks in the arch press against one another. The thrust carries down through the side walls into the foundation footing. If the spatial field cut the kiln in half along the upright plane, the arch would lose its eastern bridge pillar. The leftover half of the chimney would collapse inward within half a second, burying the kiln tender in burning coals and white-hot firebrick.”
“The whole-structure rule protects the rigger as well as the building,” Fellis realized. He nodded with deep satisfaction. “It means you can never accidentally shear a hoist line, a derrick spar. Or a foundation wall. Either the entire structure travels inside the prism, or the class remains cold.”
Kezra picked up two flat cedar shingles and laid them edge to edge on the table. She lifted the northern edge of the right shingle by half an inch. That created a raised lip along the seam.
“And here is the one-handspan height rule,” Kezra said. “When two parcels exchange, their outer edge contours must match within four inches along every foot of all four edges. If you swapped a flat square with this raised shingle, the arriving parcel would leave a half-inch lip. A human boot walking in the dark would trip. An ox cart rolling sixty hundredweight of pottery would snap its iron axle on the rebound. But if the height difference was two handspans—eight inches—it becomes an unscalable ledge. The class won’t permit an exchange that creates an artificial fracture in the ground shape.”
“Which is why ancient mapmakers cut stepped matching terraces into mountain passes,” Yseld said, her eyes gleaming with cartographic awe. “At Stonewake, at Empty Choir, and across the high saddles of the Spine. They didn’t build those terraces for beauty. They built them so their mappers could swap matching sixty-four-pace platforms without leaving a shear lip on the mountain.”
Yseld nodded slowly, her scarred fingers tracing the height lines. “That explains the ancient ruins at Stonewake. Three stepped stone benches cut into the granite pass, each sixty-four paces square, perfectly level. Travelers thought the ancients built them for sun worship. They weren’t worshipping the sun. They were cutting matching height benches so their Reach mapmakers could swap fortresses into the pass without violating the handspan rule.”
Fellis leaned back against the timber, blowing out a long breath. “Fixed squares. True north posture. Half-depth prisms. Whole buildings. And matching contours within a handspan. The class gives you huge power to move the earth, Kezra. But it ties your hands with iron rules.”
Fellis took out his horn folding ruler and checked the edge of the pine blocks once more. “Every scale is a cube cut in half,” he noted, admiring the austere proportion. “Two cubes stacked horizontally, or one cube split along its middle plane. The shape has no waste, no fancy frippery, and no weak corners. A rigger can calculate load bridles for a square prism in ten seconds flat.”
“It doesn’t tie our hands, Fellis,” Kezra said. She closed her notebook with a firm, solid snap. “It gives us the exact rules of the machine. An engineer who knows the breaking strain of every timber can build a bridge that stands for a hundred years. An amateur who guesses gets his companions killed.”