The first rib sat in its guide at the socket’s mouth, and behind it the old rib still held the socket shut.
Mara had known it since the caps came off. She had known it, she realized, since the hollow note she had heard through her palm on the first socket’s edge, the day the crew chief cut the first cap out: a note from a rib that was not quite there. The socket was not empty. Its mouth was open: the hand-finished edge, the stepped groove, the guide rail the new rib now sat on with its locating pin dropped. But deeper in, past the groove’s floor, where the socket ran into the lattice’s cage, the original rib still sat in its lock. The Founders’ rib. Four hundred years in its socket, under a factory cap, carrying a share of the cage’s load.
It had to come out before the new one could go in.
And taking it out meant unloading one section of the lattice. For the time it took to release the old rib’s lock, draw the old rib out, slide the new one in, and lock it. During that time, the old rib’s share of the load had to go somewhere. If it went to the ribs on either side, they would take the full strain of a section they had not been built for, and they were old too.
