A method for creating a watertight boundary between two graphical elements including the steps of displaying a first surface having a first shape and a second surface having a second shape on the display, an open space existing between the first surface and the second surface, defining a first region of the first surface, and defining a second region of the second surface, and modifying the first surface to a modified first surface such that the first region matches with the second region and the modified first surface and the second surface form a watertight connection at a modified first region and the second region, the step of modifying including geometrically matching the first region of the first surface with the second region of the second surface to establish the modified first region.