# How to customise (e.g. make thicker) the end-proof symbol in Beamer?

I would like to change the symbol for the end of proofs (the square) used in Beamer. It is quite thin, not very visible in some colorthemes. How can I have a thicker border and still in the structure color?

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Beamer defines the end-proof symbol in this way:

\def\qedsymbol{\leavevmode\hbox{\usebeamertemplate*{qed symbol}}}


therefore it is possible to change it by means of something like:

\setbeamertemplate{qed symbol}{...}


Defining a new symbol with TikZ:

\newcommand{\bigqed}{\tikz[baseline]\draw[ultra thick,structure.fg](0,0)rectangle(0.275,0.275);}


it becomes:

\setbeamertemplate{qed symbol}{\bigqed}


Complete example:

\documentclass{beamer}
\usepackage{tikz}

\newcommand{\bigqed}{\tikz[baseline]\draw[ultra thick,structure.fg](0,0)rectangle(0.275,0.275);}

\begin{document}

\begin{frame}
\setbeamertemplate{qed symbol}{\bigqed}
\begin{proof}
\begin{itemize}
\item First item.
\item Second item.
\item Third item.
\end{itemize}
\end{proof}

\end{frame}

\end{document}


Result:

Notice that in order to maintain the structure color of the current theme, the command uses structure.fg.

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