Template:!
Usage
This is the {{!}} meta-template.
This is an auxiliary template allowing to encode "|"
within template parameters. It is necessary if the character is used in wiki table syntax, or if the parameter is automatically wikilinked and you wish to use a pipe to specify different link text from the target page name. In other cases it is better to use "|".
This template cannot be used for putting the character as text in a wiki table; in that case, again, "|" can be used.
Note that no special template is needed for "!" (exclamation mark).
This is a high risk template, and it usually cannot be substituted (see conditions for substing on the section below).
Substitution
The template page states that {{!}} cannot be substituted. That's not completely true because it is perfectly okay to substitute {{!}} as soon as an unescaped "|" works as expected, i.e. after substituting the template containing {{!}}, or after eliminating an #if: containing {{!}}.