Manual for the tcolorbox package

3.4 Geometry
/tcb/width=〈length〉
(no default, initially \linewidth)
Sets the total width of the colored box to 〈length〉. See also /tcb/height → P. 38 .
\tcbset{colback=red!5!white,colframe=red!75!black}
\begin{tcolorbox}[width=\linewidth/2]
This is a \textbf{tcolorbox}.
\end{tcolorbox}
This is a tcolorbox.
/tcb/toprule=〈length〉
Sets the line width of the top rule to 〈length〉.
(no default, initially 0.5mm)
\tcbset{colback=red!5!white,colframe=red!75!black}
\begin{tcolorbox}[toprule=3mm]
This is a \textbf{tcolorbox}.
\end{tcolorbox}
This is a tcolorbox.
/tcb/bottomrule=〈length〉
Sets the line width of the bottom rule to 〈length〉.
(no default, initially 0.5mm)
\tcbset{colback=red!5!white,colframe=red!75!black}
\begin{tcolorbox}[bottomrule=3mm]
This is a \textbf{tcolorbox}.
\end{tcolorbox}
This is a tcolorbox.
/tcb/leftrule=〈length〉
Sets the line width of the left rule to 〈length〉.
(no default, initially 0.5mm)
\tcbset{colback=red!5!white,colframe=red!75!black}
\begin{tcolorbox}[leftrule=3mm]
This is a \textbf{tcolorbox}.
\end{tcolorbox}
This is a tcolorbox.
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