Its very simple to do and the pictures pretty much self-describe the directions to make it. Any old 2 liter plastic soda bottle will work. I made a 2 liter small one and a larger jumbo 3 liter.. But you can even use a 1 pint plastic soda bottle or even a larger water bottle of some type. The options are endless. ( elongated design ) The key with this is the flip back catch edge trough that collects the water.
2 liter soda bottle
Step 1 - cut the bottle in half using the utility knife
Step 2 - fold a 1" or 2" lip back into the inside of the bottle ( this is the trough ) Use the lighter if you need some heat to help it bend back in. Sometimes, you can do it without the lighter.
Step 3 - wet down the black rag with the nastiest water ( urine? ) you can find and set it in the sun. The nasty water will evaporate and condense on the inside sides of the bottle and find its way down into the trough.
Step 4 - when you notice enough water has collected in the trough, carefully remove the bottle from the nasty black rag and flip it over quickly.. The water now flows the other way and ends up in the cap.. Carefully remove the cap and drink the water.