---
category: Foundations
---

`hairline` is `--rule` — the navy at 10%, 1.21:1 — and `strong` is the same navy read
at the panel edge. There is no other border width: every border on the reference is 1px.

**A rule is never the only separator.** At 1.21:1 it is below every floor there is, so
the region it bounds must also change field, gain a label, or gain space. That is a ban
in the pack, not a preference.

```tsx
<Rule />
```