The centering is a wooden vault. Oak ribs, braces, a deck of boards where a mason can kneel and not fall through heaven.

Ned crawls it like a spider who pays taxes. “Stone voussoirs—the wedge-shaped rib stones—sit on this. Each one wants to fall in until the keystone arrives and they all decide to be an arch together. If you strike the centering too soon, they remember they are only wedges. If you leave it too long, you waste timber and time. Timber is a forest. Time is a feast. Both are real.”

You set a palm on an oak curve. It is warm from work, not from holiness, though the two sometimes share a room.

Wind fingers the crossing. The empty sky is a drum.

Rowan’s keystone may be in the yard, on the road, or still a quarry-shaped hope. The rib stones should be numbered. Numbers are a kindness the future extends to itself.

Strike the centering too soon and the rib becomes a handful of falling wedges. Nobody wants that picture; you still have to not do the thing that makes it. Voussoirs are numbered because the centering is a stage with marks. You are not a hero on it. You are a weight the wood agreed to hold.