\setbox0=\hbox{\vrule height2pt width0pt\vrule height1pt width1pt\kern2pt}
\def\tri{\setbox0=\vbox{\hbox{\kern.5\wd0\copy0}\hbox{\copy0\copy0}}%
  \vbox{\copy0\vskip12pt}}

{\offinterlineskip
\hbox{\tri\tri\tri\tri\tri\tri}}