Abstract: A system and method for installing trim around a window in a construction application where the jambs of the window are not as wide as the wall in which the window is being installed. The system uses jamb mounting elements attached to the jambs of the window. Trim mounting elements are either attached to the trim or its functional equivalents milled into the wood of the trim. When the trim is mounted to the wall surrounding the window, the jamb mounting elements and the trim mounting elements overlap, thereby eliminating any gaps between the trim and the jambs of the window. By overlapping the jamb mounting elements and the trim mounting elements, these two elements can be adapted to fill in the gaps between the trim and the window jambs across a large range.