This a a *TeX question... and actually not too hard to answer
The simplest \usepckage{zed-csp.sty} and then the symbol is \interleave (as you
would expect if you know CSP). Expanding macros tells you \interleave is
equivielent to
\mathrel{\mathord{\mid}\mkern-2mu\mathord{\mid}\mkern-2mu\mathord{\mid}}
if you want two lines then examine \parallel in the same package.
--
Duncan (-:
"software industry, the: unique industry where selling substandard goods is
legal and you can charge extra for fixing the problems."
