Helper lines
Helper lines help you to lay out and align content on a dashboard. The horizontal and vertical helper lines become visible at defined points on the background when hotspots at the edge or center of a widget approach them - for example, when you drag or resize a widget.
Lines are displayed at these points on the X and Y axes of the dashboard: 0.333, 0.5, 0.666. So, for example, you could resize a widget to occupy precisely a third of the dashboard.
To turn helper lines on or off: