Supplies: Food storage container, with one being 50% taller and about 2" wider (diameter) or 1"x1" WxD larger if square. (i.e. 4" diameter, 3" tall for one, and 6" diameter, 4" tall for second) Krylon Fusion Flat Black Spray Paint Pastic cutter, Dremel, or utility knife sharpie or other way to mark your work adhesive to connect plastics Figure 1 Figure 2 Figure 3 Figure 4 Steps Remove the tops from both containers. (Figures 1 and 2 give example sizes for demonstration purposes) mark a line the size of your intake exhaust line on the inside of your smaller containers lid, making it no bigger than 1" smaller on every side cut out marked in area (refer to figure 3) center the smaller lid on the larger one and transfer the cut mark to the larger lid and cut it out as well, and attach them together (figure 3) Using the picture as a guide, cut slots out of the larger containers sides that are half as tall as the smaller container, starting from the top of the container. (Figure 4, containers shown upside down.) Turn the smaller container upside down, and cut slots out of the bottom of the container (refer to figure 4) paint insides of lids and containers, as well as outsides optionally, and allow to dry (1 hour) Attach the lids to your vent/intake surface, then attach small container then large container. (Figure 5, below) Figure 5 - Assembled optional: if you cut slots rather than a hole in the larger containers lid you can pack carbon material inside pantyhose/cheesecloth inside the smaller container for even more assured light leak prevention as well as odor control. tip: this can be scaled to any size you need, really. You can even use trash cans, if you need a super sized light trap. tip 2: air can flow either way. The flow diagram above is just an example. Edit: Added better quality images.