1 \documentclass[a4paper]{article}
6 \def\iwjtest{{/\mkern-9mu\Sqsupset}}
7 \newcommand{\iwjtestx}{\mathrel{\ooalign{$\Sqsubset$ $\sslash$}}}
8 \newcommand{\iwjtesty}{{%
9 \declareslashed{}{\sslash}{-0.04}{0}{\Sqsubset}\slashed{\Sqsubset}}}
12 $ A \not \sqsubseteq B $