The surveyor hit a rock six inches down and moved the pin left. The lot line shifted. The oak tree that had been on the Mercers' side was now on the Doyles'.
The Doyles built a deck around it. The Mercers built a fence along the new line. The fence defined the yard. The yard defined where the kids played. The kids wore a path between the gate and the oak tree, and when the city paved the alley twenty years later, they followed the path.
The path is now on maps. The maps are in databases. The databases route ambulances.
The surveyor retired to Tucson. She doesn't know about the oak tree. She knows she hit a rock, and that the ground decides where the pin goes more often than the engineer does.
She'd say the same thing the painter said about the river. You put it where it lets you.