I would like to add a link to the bottom of all posts for unregistered users inviting them to register so that they can reply to posts. Which template would this go in?
Thanks,
John

showflat

If you just want a generic post that shows a link you could put it in the html includes section and add it to the footer.
However if you have say a post that has no replies, it would be out of view on the initial visit,then the best course would be to edit the template as Sirdude suggested.

Thanks, I added it to the showflat template and it gives me what I need.