A book has a folio because it remembers your hand. The page number is not a count — it is the reader’s grip on the spine, the only gesture that survives the migration from sheet to screen. We have shipped editions whose chapters were unnumbered; we have not shipped one whose folio was missing. The folio is the only word on a page that knows where it is.
The chapter rail is a spine.
On the homepage, the chapter rail runs the height of the viewport, set at 3.5% width on the left margin, hairlined at the top and bottom, with the chapter numeral inset in oldstyle. The rail is not navigation. It is a presence. The reader’s eye is meant to register it the way a hand registers the spine — without naming it, without using it, but without forgetting it is there either.
We tried to make the rail clickable. It scrolled. It animated. It glowed. We removed every behaviour, one by one, until the rail did nothing. It is better silent. The reader knows where they are without being asked.
A folio is the only word on a page that knows where it is. Trust the folio. The reader’s thumb does.
The running folio is a horizon.
Across every route, the running folio sits at the bottom-right of the viewport, set in oldstyle at 9pt, paired with the volume’s roman numeral in small caps. It updates on scroll: not as a counter, but as a horizon line — the reader is always somewhere, always between, always between an opening and a closing the layout has agreed to acknowledge.
We chose the bottom-right against the convention. Most pages run the folio centred, or in the running header. Centred reads as a chapter opener. Headers compete with the title. The bottom-right is what the eye lands on when the page finishes — it is the receipt. We have run it elsewhere. We have come back.
A note on the scroll.
Scroll is not a page-turn. Scroll is the metaphor we inherited from terminals and never argued with. The folio, on the chrome, is the only piece of the layout that pretends otherwise — it advances in discrete steps, snapping at each chapter boundary, refusing to update continuously. The refusal is the page-turn. The rest is scroll. The folio is the only part of BFS that still keeps a book’s time.