So, I want a dashed line to separate the different repeater items in my client's newsletter.
But what I don't want is a dashed line after the last item.
How do I specify an item as a "top" or "bottom" if it is a repeater? I see the code in the sample template. But I don't know how to incorporate it.
When you say you can see the code in the sample, can you let us know what code specifically you are referring to? If it just a class being added, then it is likely to not be a repeating element, but a single editable element instead.
What you probably need is the http://reference.sitepoint.com/css/pseudoclass-lastchild last child pseudo class, but unfortunately we haven't done a lot of testing to see how well supported it is.