Cfrgtkky

I have difficulty writing a compact command that allows me to insert a text between two lines.
I read some links such as this and this, but each one treats the left and right line separately

documentclass{article}

usepackage{amsmath} %<<=== 

usepackage[normalem]{ulem}

usepackage{xcolor}



newcommandgsout{bgroupmarkoverwith{textcolor{gray}{rule[0.5ex]{2pt}{2.5pt}}}ULon}



newcommand*{sxrule}[1][3em]{textcolor{gray}{rule[0.5ex]{#1}{2.5pt}};}





begin{document}



sxrule Osservazioni gsout{hfill}



end{document} 

Have any suggestions? thanks

Perhaps something like this:

Here's the code:

documentclass{article}

usepackage{xcolor}

usepackage{lipsum}



newlengthsxrulelength

newcommandsxrule[2][3em]{%

  settowidthsxrulelength{,#2,}%

  noindent%

  textcolor{gray}{rule[0.5ex]{#1}{2.5pt}},#2,%

  textcolor{gray}{rule[0.5ex]{dimexprlinewidth-sxrulelength-#1relax}{2.5pt}}%

}



begin{document}



  lipsum



  sxrule{Osservazioni}



  lipsum



end{document}

The sxrule macro has an optional argument that controls the length of the "left hand" line. As in the OP, this defaults to 3em.

Judging from the comments, perhaps the definition

newcommandsxrule[2][3em]{%

  settowidthsxrulelength{,#2,}%

  noindent%

  textcolor{gray}{rule[0.5ex]{#1}{2.5pt}},textbf{#2},%

  textcolor{gray}{rule[0.5ex]{dimexprlinewidth-sxrulelength-#1relax}{2.5pt}}%

}

is better as now sxrule{Osservazioni} puts "Osservazioni" in bold:

documentclass{article}

usepackage[normalem]{ulem}

usepackage{xcolor,lipsum}

newcommandfilrule{{color{gray}{leaders

hrule height .7ex depth -.4ex  hfill }hskip .0em}}

defruledworld#1{bigskipnoindentfilrulequad%

#1quadfilrulebigskippar}

begin{document}

ruledworld{Osservazioni}

lipsum[2]

ruledworld{Grandi conclusioni}

lipsum[3]

end{document} 

If you do not want the word centered but start at a fixed point, change the first filrule in the definition of ruledworld by a normal rule. Or You can left a single filrule on the left, but a few on the right (e.g., filrulefilrulefilrule) to have the word centered with respect some point (at the 25% of the line, in that example).