For Do-It-Yourself, or retrofit any of the 102 Series Guerrilla Boxes™ (5x7 Pocket Box™, 6x8 ThumBox™,8x10 Cigar Box™, 9x12 LapTop Box™). Holds two panels (back-to-back) in the larger space and one more in the front. Extends in front of the bottom edge of the open lid.