Anyway to cut a long story short, I became somewhat stuck as to what I wanted to name the class they share. All I could come up with was Xer, HeaderFooter and sandwich. Similar word groups like 'suffix' and 'prefix' give me the same issue, coming up with Xfix which is just awful nomenclature!
What categorically describes both headers and footers?
Further edit: I want to emphasize that I am not concerned about the web design/coding aspect of this at all. I could easily just name it div.CantThinkOfName if that were the issue. I'm referring to header/footer as it applies to any document or setting in the English language.
Final Results: Best coinage is Running Marginals. I've chosen Running Sections as the correct answer as this phrase is already in use while awarding bounty to Marginals (which eventually became running marginals) as this is a more relate-able terminology.