Template:sigbox raw
From Homestar Runner Wiki
{{{1}}}
Usage: {{sigbox raw|Text}}
to put the text in a box.
You can try {{sigbox raw|{{User:Username/sig}}}}
to put a template-ized sig inside the box, but {{sigbox}} is simpler.
One use for this could be to put <noinclude>{{sigbox raw|1=</noinclude>
and <noinclude>}}</noinclude>
around your sig in the template itself (so you can easily see its size in Show Preview). The 1=
bit protects it from being confused by any =
signs in the sig (it still will get confused if you have any |
signs outside of links), but you can use {{!}} for those.