The VT420 displays a two-pixel divider line when switching screens. For a dark screen half, the divider line is bold (not just foreground), and for the light screen half, the divider black.
Two dark sessions results in two bold lines, while two inverted sessions are two dark lines.
The status line appears to move down by two pixels when these divider lines are enabled.

The VT420 displays a two-pixel divider line when switching screens. For a dark screen half, the divider line is bold (not just foreground), and for the light screen half, the divider black.
Two dark sessions results in two bold lines, while two inverted sessions are two dark lines.
The status line appears to move down by two pixels when these divider lines are enabled.