Tie one end of the water filtering bag tightly closed, and the other end is tied to hold the bag-like device from a low-hanging strong tree limb.
Place several inches of new medium-ground charcoal (cold, from your campfire pit) into the bag first. Layer-in several inches of clean sand. This will hold the charcoal in place.
A next layer is small-to-medium gravel and pebbles. Again, this hold the sand in place. Another primary layer of clean filtering sand and a primary layer of pebbles and small gravel complete the water filter. Study the image to know the sequence.
Finally, using a can or bottle, add the raw water to the open end of the water filtering bag. This will take quite some time for the water to percolate down through the layers before you begin to see drippage. You will need to add more water a few times before you see any results, but eventually clean drinkable water will come through the layers and leak out of the bottom where the bag is tied-off.
This water will be fit to drink, having been filtered by the multiple layers of sand and charcoal. Once the filtering layers have been wetted the first time, adding more water will cause filtered water to come out more quickly to satisfy demand.
For it is worth mentioning, if you are stranded in your car without these provisions to build a water-fitlering system, you still have options. Removing the hubcaps from your car (especially metal hubcaps) and wipe the interior clean with your shirt or a cloth. Leave them out overnight where condesation and ice crystal might form. Early in the morning, check these. You might have enough frost and dew to provide a swallow of water. Even this little bit is better than nothing at all in a survival situation.
