Template:((
Outputs a literal double open curly brace ({{) as plain text, escaping it so it doesn't get parsed as the start of a template call. Used inside documentation and usage examples to display raw template syntax without it actually executing — exactly the pattern used in the real MediaWiki {{Ll}} documentation you pasted earlier, e.g. {{{{ll|Project:About}} to show a literal without transcluding it.
{{Project:About}}
Usage:
{{((}}CaseInfobox{{))}}
Renders as:
{{{name}}}
— displayed as plain text, not a working link or transclusion (compare to {{Tl}}, which does link)
Parameters
None — this template takes no input, it just outputs {{.