It is possible to collaborate not only over shared interests, but also over interests that, while
different, do not
conflict. These differences can work in balance and, at best, in complementarity. So “dovetail[ing] differing interests” allows everyone to get what they want in an equal, balanced way. The author’s previous anecdote of the librarian opening the window in the next room is an example of this. But dovetailing is only possible when negotiators have a clear and reliable idea about the other side’s interests and are willing to explore creative ways of meeting them.