Template sigbox raw
{{{1}}}
Usage: Template:Sigbox raw to put the text in a box.
You can try Template:Sigbox raw to put a template-ized sig inside the box, but {{sigbox}} is simpler.
One use for this could be to put Template:Sigbox raw 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.