Questo è l’inizio di [tt]placeins.sty[/tt]
`\@ifundefined{DeclareOption}{}%
{\DeclareOption{below}{\def\@fb@botlist{}}
\DeclareOption{above}{\def\@fb@topbarrier{}}
\DeclareOption{section}{\AtBeginDocument{%
\expandafter\renewcommand\expandafter\section\expandafter
{\expandafter\@fb@secFB\section}%
\newcommand\@fb@secFB{\FloatBarrier
\gdef\@fb@afterHHook{\@fb@topbarrier \gdef\@fb@afterHHook{}}}
\g@addto@macro\@afterheading{\@fb@afterHHook}
\gdef\@fb@afterHHook{}
}}
\DeclareOption{verbose}{\catcode`\V=9 }% Activate things after `V'
\ProvidesPackage{placeins}[2005/04/18 \space v 2.2]
\ProcessOptions
} % end of \@ifundefined`
Quindi la ridefinizione è opera di [tt]\usepackage[section]{placeins}[/tt]
Ciao
Enrico