I am trying to reproduce the following:
My best attempt so far uses skak.
\begin{figure}
\newgame
\showallbut{P,p,K,k,R,r,Q,q,B,b,N,n}
\showboard
\caption{The Frontier Line}
\end{figure}
How to add the central line?
Note: Please do not consider font, caption…


\chessboard[showmover=false, pgfstyle=topborder, markregion={a4-h4}, label=false]– Nov 12 '19 at 21:36