# \rule command constructing line not extending far enough left

I am trying to put a horizontal line between homework problems, like this:

\begin{description}
%stuff . . .
\rule{\linewidth}{0.4mm}
\item[Exercise 1]
%stuff
\rule{\linewidth}{0.4mm}
\end{description}


If I knew how to get this to display on this website, you would see that the line begins over the second 'e' of 'Exercise', and looks off, as one would like the line to be exactly aligned over the capital 'E'. Does anyone know how to do this?

-
Try \hspace*{\dimexpr-\labelwidth-\leftmargin\relax}\rule{\linewidth}{0.4mm} –  Peter Grill Mar 9 '12 at 0:47
That translates the whole line left, leaving the right side of the text "un-underlined". –  Nick Thompson Mar 9 '12 at 1:00
Of course, I forgot to adjust the right hand side: \hspace*{\dimexpr-\labelwidth-\leftmargin\relax}\rule{\dimexpr\linewidth+\label‌​width+\leftmargin\relax}{0.4mm}. But solution below seems to work just fine. –  Peter Grill Mar 9 '12 at 1:05
Ah! That works! Thanks. –  Nick Thompson Mar 9 '12 at 1:28

This is a bit of a kludge, but it seems to work.

\documentclass{article}
\usepackage{showframe} % as per PeterGrill's suggestion
\newcommand{\fullwidthline}[1]{\hspace{\itemindent}\rule{\textwidth}{#1}}

\begin{document}
\begin{description}
\item[Exercise 1] ...

\fullwidthline{0.4mm}
\item[Exercise 2] ...

\fullwidthline{0.4mm}
\item[Exercise 3] ...
\end{description}
\end{document}

-
Thank you very much! That worked perfectly. (I would accept this answer but I don't have enough rep!) –  Nick Thompson Mar 9 '12 at 0:49
Excellent!!. If you add \usepackage{showframe} you get a nice image to show that the line is indeed the full width. –  Peter Grill Mar 9 '12 at 1:06
neat! Didn't know about that package :) –  huon-dbaupp Mar 9 '12 at 1:09