A roller shade adapted to adjustably cover a structural opening comprising a roller tube assembly having a roller tube and a shade material attached to the roller tube, a pair of longitudinal side panel assemblies adapted to be attached at opposite sides of the structural opening and retain the roller tube assembly therebetween, at least one lateral panel comprising a side wall having an alignment channel recessed in its outer surface, and at least two corner brackets. Each side panel assembly comprises a tensioning assembly adapted to tension the shade material. Each corner bracket comprises a first portion and a second portion orthogonal to the first portion. The first portion is adapted to be attached to one of the longitudinal side panel assemblies. The second portion comprises a substantially flat wall with an alignment tab linearly extending from its terminal end. The alignment tab is sized to fit within the alignment channel of the lateral panel. The lateral panel is installed to the structural opening between the pair of longitudinal side panel assemblies by aligning and inserting the alignment tabs of the corner brackets into the alignment channel of the lateral panel and attaching the lateral panel at a head or base of the structural opening.