System dividers on dense multi-system pages

On a page with several systems stacked closely, a short diagonal double-tick mark is placed at each system's left margin to separate it from the system above when the vertical gap alone risks reading as ambiguous.

Multiple barsPerSystem-wrapped systems rendered with insufficient vertical gap that no divider or extra whitespace compensates for.

Gould (Behind Bars, system layout / page-density conventions).

This rule is about where marks land on the page, so it can only be judged after engraving. Collision and spacing faults live here.