In the texbook, the hash mark symbol is obtained with the sequence \# which produces this.
\documentclass[border=2mm]{standalone}
\begin{document}
\#
\end{document}
But on the texbook itself, there is the hash mark preceded by the backslash \which does not have the same form as the one obtained.
How to get the texbook symbol here underlined in yellow?



\texttt{\#}? – moewe Dec 27 '19 at 10:14