What are the diagonal lines in boxes? - Cousin Smart

When distant cousins marry, they may appear in more than one place on a chart.

Duplicate persons on the chart are shown in each location, highlighted in boxes with horizontal gray line fill.

However, the lineage is only continued on one branch, from that point on the chart, to conserve space. This is Progeny's Cousin Smart option in action.

This condition is also know as "pedigree collapse", or "implexus".