Margin

Tier

directive

Surfaces

page

Fallback

literal

State

settled

The strip beside a page's text, where a reader can be told where they are — part of the document, not chrome around it.

:::margin
::contents
:::

Placement is containment, never an attribute. A block stands in the margin because it is written inside :::margin. There is no place= anywhere in this format, and no block has a second spelling for a margin form.

At most one per page, written at the top level. A second :::margin is ordinary content, drawn in flow and unchanged in the file — nothing is lost and nothing is refused.

It holds the blocks a column holds, and changes where a block is drawn, never what it is.

It is the right-hand side only, and not by symmetry: the left margin is already spoken for by a block's drag grip and by rectangle selection. Where there is no room, its content falls into the flow at the point it stands in the file — never behind a control, because content that vanishes with nothing to press is content lost.