/usr/share/doc/texlive-doc/plain/metatex/mtpaper/frame.tex is in texlive-generic-extra 2013.20140215-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | % FRAME.TEX (RMCG19950401)
\catcode`\@=11
\newbox\@uxbox
\let\oldhrule=\hrule \let\oldvrule=\vrule
\def\rulethickness{\afterassignment\rul@thickness\dimen0 }
\def\rul@thickness{\edef\hrule{\oldhrule height\dimen0 }%
\edef\vrule{\oldvrule width\dimen0 }}
\def\framebox{\afterassignment\fr@mebox\count@=}
\def\fr@mebox{\ifvoid\count@\else \bgroup
\dimen0=\wd\count@ \dimen2=\ht\count@ \advance\dimen2\dp\count@
\global\setbox\@uxbox=\vtop{
\hbox to\dimen0{\vrule\hss\vbox to \dimen2{\hrule\vss
\hbox to\dimen0{}\vss\hrule}\hss\vrule}\kern0pt}\egroup
\wd\@uxbox=0pt \ht\@uxbox=0pt \dp\@uxbox=0pt
\ifhbox\count@
\setbox\count@=\hbox{\raise\ht\count@\box\@uxbox\box\count@}\else
\setbox\count@=\vbox{\box\@uxbox\nointerlineskip\box\count@}\fi\fi}
\catcode`\@=12
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