This is an auxiliary template allowing to encode " | " within template parameters. It is unnecessary to get a " | "; " | " is a better choice for this purpose. However, the " | " delimiter for a Wiki table must be escaped by a template for use within a template; see also WP:QIF .

Note that there's no such problem with " ! " (exclamation mark), it only affects " | " (vertical bar) in conjunction with the m:Help:Parameter_default mechanism within tables.

For obvious reasons this is a high risk template , and it cannot be substituted .