An mdl/option/tool used when working in 2D files. It would showed a rectangle in a user designated view (i.e. View 5 (with overview of everything in the file/project)), showing the displayed area of a user selected view (i.e. View 1). It would be dynamic meaning the Rectangle would move/resize in View 5 to show the designated view (i.e. View 1 (working view)). So as you windowed/paned/zoomed/rotated the view, in View 1, the Rectangle would change in View 5 showing the area shown in View 1. The user could pick the Color weight and Style of the Rectangle along with the view to display the rectangle in and the view the rectangle reflected..