I'd like to create code pages for "header" and "left nav column" and "right nav column" and "footer" and then utilize them across all the various template pages within the same template.

That way, my default, home, sitenews, search results, etc, could all share the same, say, "right nav column" and a single change to it would cascade down to all of them.

Is that doable in the way template pages are handled? Is there an allowance for an "include" page, or some such?