Before we get started, it is illegal to use spring snares in the UK. So why are we posting details? It’s a fun engineering project. Once you’ve made one and tested it, take it back down.
Snares are still legal as a means of hunting in the UK, but the snares must be used only to catch (not kill) the animal, and the eyes must be free running, and not locking or sprung. They must slacken off when the animal stops struggling. It’s also important to be aware that you must check a snare at least daily, and that certain animals cannot be caught by snare (including red squirrels, otters, pine martens, hedgehogs, badgers and domestic animals). Snares must be firmly attached to the ground and not used in such a way as the animal is hung or suspended when caught. The laws in Scotland are more restrictive, and snare users must obtain a registration number from the police which must be placed on the snare.
The main purpose for using a spring with a snare is to lift the animal into the air and away from predators. All you need to make the snare is a good knife, nylon string (the inner cords from paracord are ideal), a live bending sapling and some sticks.