The U.S. military's term for using natural objects to accomplish a task is field expedient (FE). If you're lost or stranded in the wild and you have no materials at all, you'll need FE tools and shelter.
FE shelters employ the same methods as ones built with ponchos or tarps. The only difference is what you use to cover the frame. After you build the frame, use branches and thicket to make up your roof. Pine boughs make for good insulation, but as long as you stack and weave lots of leaves, branches and twigs, you'll have adequate shelter. Think of your shelter roof as being shingled like a house. Work in layers from the ground up and keep the branches pointed toward down for rainwater runoff.
A debris hut is an FE shelter that's easy to build and provides great protection from the elements. To build one:
Place a ridgepole, the pole that runs the length of the shelter, with one end on the ground and the other on top of a sturdy base like a tree stump or boulder. You can also lash it to a tree.
Take two more thick branches and place them diagonally at the top of the ridgepole and lash them together with vine.
Use thick branches to line the length of the ridgepole to create the ribbed frame. Make sure it's wide enough to accommodate you.
Place smaller sticks crosswise to make a lattice effect.
Add lighter soft debris like pine needles and leaves until it's at least two feet thick -- the thicker the debris, the more protection it offers.
Cover the interior floor with pine and leaves and block the entrance with a rock or more debris.
A debris hut provides great protection in cold conditions. If you're in deep snow and have large evergreen trees around, build a tree-pit snow shelter:
Find a thick evergreen tree with low-hanging branches.
Dig down into the snow to your preferred depth and diameter -- the cozier the better.
Pack the interior snow well.
Use the natural branches above and add additional boughs for your cover.
Use boughs as insulators on the interior floor.
A tree-pit snow shelter takes a lot of energy to build, but it's a great insulator against frigid weather.
Some other tips to remember:
If you want a fire, it's best to keep it outside or near the mouth of the shelter. In extreme conditions, you can bring the fire inside, but it should be well-ventilated, and the flames should not be near the shelter walls.
Heat up rocks in the fire and stack them inside the shelter for extra warmth.
Always turn off your stove or lantern inside your shelter -- dangerous carbon monoxide gas can kill you.
Found metal isn't good to use for roofs. It will deflect rain and wind, but also reflect needed sun for warmth.
Snow is a great insulator, so use it as much as possible.
Pour water over thatched roofs in freezing weather -- this will ice over into a hard, protective insulator.
Whatever your emergency scenario, the most important thing is to remain calm and in control.
Panic will get you nowhere and knowing some rudimentary survival skills can be the difference between life and death. Basic shelters are easy to build and crucial to surviving the harsh elements of the great outdoors.
If you're an avid camper or hiker, you should practice building a shelter on your next excursion. It can be educational, potentially life-saving and a lot of fun.
The above is an excerpt from:
Charles W. Bryant. "How to Build a Shelter". December 29, 2007 http://travel.howstuffworks.com/how-to-build-a-shelter.htm (January 13, 2008)
To make a Hobo Mattress, you fill two large plastic garbage bags about half-full with newspaper, leaves, or whatever is handy and soft. Duct tape the open ends together to make a huge pillow. Cut the corners off (about 1 inch vent holes) to let the trapped air out. Nice and comfy.