I used B&W 6 mil poly, some tarp zippers and a roll of 1" wide velcro. I made two doors, open the first one, and there's a second one right behind it, so double the light block Tarp zippers on both sides, velcro to seal the bottom, there is NO light getting through. I also made a 4" flap between the two doors, around the edge, to cover the zippered area as another level of light proofing. I am in a wood box i built, framed with 2x3's, so i was able to staple the B&W up, but if you go to the tarp section of a hardware store they sell do it yourself grommet kits, put some grommets in the B&W, use zip ties to hold it up in the tent. Then seal around the edges with tape. Stick the tarp zippers on where you want your door and then cut, add velcro to the bottom to seal. I went around and stapled the zippers and velco as an added attachment, i was worried the heat in the room would eventually loosen the adhesives.