This template must be substituted. Replace {{{{{1}}} with {{subst:{{{1}}}.
Usage
In a template that must be substituted, add the following code at the top:
{{ {{#ifeq:{{<includeonly>subst:</includeonly>void}}|{{void}}|void|Error:must be substituted}}| template name }}
Example: Template:Demo of template that must be substituted (backlinks edit).
{{Demo of template that must be substituted}} → This template must be substituted. Replace {{Demo of template that must be substituted with {{subst:Demo of template that must be substituted.Template body
while {{subst:Demo of template that must be substituted}} gives "Template body".