Wave rails test box
The rail dots should never paint over the bottom divider.
Second box for height testing
Open and close boxes, then resize. Rails should remain under the divider.
V rails test box
Dots should stop before the bottom divider begins.
Inverted-V rails test box
The bottom divider should remain above rail dots at every width.
This section has no rails. The bottom divider should still scale cleanly on resize.