property Surface.BorderWidth as Long
Sets or retrieves a value that indicates the border width of the control.

TypeDescription
Long A Long expression that specifies the width of the control's border where the element that does not fit the control's visible part are shown.
By default, the BorderWidth property is 2 pixels wide. The BorderWidth / BorderHeight properties specify the size on the margin where the overview elements are shown. The OverviewColor property specifies the color to show the elements when they do not fit the surface's visible area. The OverviewColor property has effect when the element is not fitting the surface's client area and it is shown on the border of the surface.

The following screen shot shows the how elements are shown when they are not visible in the surface's client area ( look on the border ) :