Mansfield Long-Range Background. From Stan Weinstein's book.
This plots the high-low range for the last N years, including the current year.
It gives us an idea of any long-term resistance or support in play, which may affect how a trend behaves.
Note that one could just as easily check the yearly chart to get what this is showing, but it's convenient to have a template with all the elements required to emulate a Mansfield chart.