Bar Line charts are useful for spotting trends and comparing items against one another as well as showing comparisons between metrics. For instance, you might have bars that represent the number of employees per department, and a line that indicates productivity; or bars that represent software product sales, and a line that represents the number of evaluation downloads. You cannot have more than one line per bar line chart, so if you need to compare more than one set of metrics, you will have to create multiple charts to show them.