Step 1. Build in a fringe area, neither in the center of a field nor a dense thicket, but somewhere between these areas. Choose an area at least 50 yards from a body of water, as evaporating water tends to add extra chill to the air.Step 2. Find a fallen tree or a large, long rock to build your lean-to against. You can also tie a branch horizontally between two trees a few feet off the ground. The important thing is to have a sturdy brace to lean your structure against.Step 3. Lean stout sticks along the horizontal brace of your lean-to. Crawl beneath them to make sure there is enough room to sleep under. There shouldn’t be too much extra room, but it should be long enough to cover you completely.Step 4. Pile smaller branches and twigs on top of your stout branches, leaving only an opening at either end exposed.Step 5. Pile all manner of debris – moss, leaves, pine needles, dried fern or whatever nature makes available – on top of your structure.