The toplevel header of a OurBigBook file is its first header and the one with the lowest level, e.g. in a document with recommended syntax:the header
= Animal
== Dog
=== Bull Terrier
== Cat
= Animal
is the toplevel header.Being the toplevel header gives a header some special handling described in child sections of the section and elsewhere throughout this documentation.
The toplevel header is only defined if the document has only a single header of the highest level. e.g. like the following has only a single
h2
:== My 2
=== My 3 1
=== My 3 2