> For the complete documentation index, see [llms.txt](https://overleaf-pro.ayaka.space/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://overleaf-pro.ayaka.space/latex/tex-latex-primitives/07-overfullrule.md).

# \overfullrule

`\overfullrule[=]` *dimension*

Where:

* “`[=]`” means that the equals sign is optional.
* *dimension* is an amount specified in units that TEX can understand—e.g., pt, bp, mm etc.

When TEX detects that an hbox is overfull—such as a line in a typeset paragraph or some text in an `\hbox{..}`—it will write that information to the log file. In addition, TEX engines also provide the `\overfullrule` command which can be used to instruct TEX to add a short rule to the end of the offending box, acting as a visual warning to the user.

**Usage example**

Because the “=” sign is optional you can write `\overfullrule=10pt` or `\overfullrule 10pt`.

Note that LATEXsets `\overfullrule` to 0pt, Plain TEX sets it to 5pt.

#### An example

We’ll use an `\hbox{}` that will be overfull: `\hbox to 10pt{This box will be overfull}` and set `\overfullrule` to a non-zero value, say 10mm:

```
\overfullrule=10mm\hbox to 10pt{This box will be overfull}\par
```

The following graphic shows the output:

![](/files/eXIN40lByc9HHLWi2L9C)

As you can see, a 10mm-long rule has been added to the end of the overfull `\hbox`. Now set `\overfullrule=0mm` to prevent an overfull box rule being displayed:

```
\overfullrule=0mm\hbox to 10pt{This box will be overfull}
```

The following graphic shows the output:

![](/files/B2PKDlvPmg9GPcsYD34q)

The resulting `\hbox` is still overfull but this time it is displayed without an overfull rule to highlight that fact.

#### Another example: lines in a paragraph

When TEX breaks a pararaph into lines of typeset text, each line in the paragraph is stored in an `\hbox`. TEX can be told to display overfull lines by setting `\overfullrule` to a non-zero value. The following example shows overfull rules being displayed at the end of overfull lines in a paragraph.

To create a paragraph, we’ll put some text in a narrow `\vbox`, set `\overfullrule=10pt`, and draw the box with a border. Note that because we used the `\verb` command we first need to save the `\vbox` in a box register (100) and then use the LATEX command (macro) `\fbox` to draw a tight border around it, making it easier to see the overfull lines.

```
\overfullrule=10pt
\setlength{\fboxsep}{0pt}% To ensure a tight border with no gap
\setbox100=\vbox{\hsize=30mm Inside this vbox we’ll set the
linewidth to 30mm using \verb|\hsize=30mm|.
We are typesetting some text inside a \verb|\vbox|
because it will cause \TeX{} to perform linebreaking
and build the paragraph as a stack of horizontal boxes.
For some lines \TeX{} might be unable to find a good
linebreak which can result in lines too wide to fit
within a width of 30mm. Because \verb|\overfullrule| is
non-zero (10pt), those overfull lines are
indicated by an overfull rule of width 10pt. Note that to \TeX{},
this box is still considered to be 30mm wide even though
some lines do not fit and an \verb|\overfullrule|
of width 10pt is added on to the end of some lines.}
\fbox{\copy100}
```

The following graphic shows the output:

![](/files/TRbClsY2X2V7srgCO1JA)


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