This template should be placed on the documentationsubpage (not the template page itself) of any template that may be substituted (but may also be transcluded).
Parameters
This template accepts one optional parameter, which can be used to give a more detailed description of why the template in question should not be substituted. For example, {{May be substituted|Example text.}} produces:
{{substituted or transcluded}} – if-then-else metatemplate that checks if a template is currently being substituted or transcluded
{{always substitute}} – For the doc of the above templates; prints a message asking for it be substituted.
{{never substitute}} – The reverse of {{always substitute}}. For the doc of templates which should not be substituted; prints a message asking for it not to be substituted.
{{may be substituted}} – For the doc of templates whose substitution is optional.
{{substitution}} – Allows free-fill description of whether the template should be substituted and under what conditions.