In post-fall-of-society, survival-centric world, it will be imperative to know certain skills by which to survive. Some of the most essential skills will relate to hunting, fishing, and trapping. While it is legal in most (possibly all) states if properly licensed, trapping in a survival scenario is a very effective and efficient way to harvest food from nature. Rabbits, squirrels, even fish can be caught with a properly-built trap.
My personal favorite small-game trap is the snare. The two most common types of snare are the spring-snare and the dead-fall. The spring-snare relies on some flexible ingredient, most-commonly a young tree (though I’ve seen a fiberglass fishing pole used for this as well). The deadfall snare uses a counterweight, such as a rock or log.
The idea beind either of these snares is that you create a small perimiter out of your snare line, and build a sensitive trigger system over top. If the twig that triggers the snare gets stepped on or moved at all, the trap will engage and slip-knot the animal’s foot or head. The trap engages by either letting the flexible tree snap back, or by allowing the counter-weight to fall.
Rather than try to draw diagrams or describe it with text, I will embed a really good video I found that describes very nicely how to build a spring-snare from nothing more than some sticks, a sapling, and some type of thin line (twine, string, etc).