# Douglas Stebila

# LaTeX Blackboard Bold 1

June 27, 2004 at 04:55PM Computers

A request to my math-oriented readers. Does anyone know how to do a good blackboard bold 1 (one) in LaTeX? The simple `\mathbb{1}`

doesn't work because the numbers aren't defined in the mathbb font. I've come up with the following hack but it's not perfect, because it's not actually a font glyph but a 1 with a line. If you've got a better way, please let me know.

```
\newcommand{\1}{ {\rm 1\hspace*{-0.4ex}\rule{0.1ex}{1.52ex}\hspace*{0.2ex}} }
```

**Edited to add comment from reader Phil Armstrong:**

```
\documentclass{article}
```

\usepackage{bbold}

\begin{document}

${\mathbb 1}$

{\textbb 1}

\end{document}