This feature is primarily applicable to the Summit HX Series and Wall Displays that use monitors (instead of projectors). If one imagines standing in a living room and looking outside through a large, multi-pane picture window, it is obvious that the frames (shown in light brown) of the individual window panes will obscure part of the scenery. With a SingleLogicalScreen display that stretches over several monitors, this "window pane" effect can be configured in the HX Series (with the frames being the monitor borders). The two pics below illustrate a section of a wall display where four monitor corners come together:

Note that there are applications in which neither of these two effects are desirable. Air Traffic Control is an example. Hiding airplanes behind the monitor borders would not be a smart thing to do, and the typical adjacent monitor effect can cause confusion trying to follow the many track lines through the "breaks," also not a good thing. Hence, for ATC, the solution that is used is to provide very large, high resolution flat-panel monitors.