%% 
%%  Example 02-01-1 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{158.31393pt}
\setlength\parindent{0pt}
\AtBeginDocument{%
\abovedisplayskip=0pt
\abovedisplayshortskip=0pt
\belowdisplayskip=0pt
\belowdisplayshortskip=0pt}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{align}
y &= x\makebox(0,0){\rule[-2.2cm]{0.2pt}{1.5cm}}
\end{align}
\begin{align}
y \makebox(0,0){\rule[-1.5cm]{0.2pt}{1.5cm}}=& x
\end{align}
\begin{align}
y ={}& x
\end{align}
\end{document}
