The exclusionary traps (leg hold traps) are designed to capture the leg of a raccoon or opossum that reaches into it to find food.

For years, New Jersey fur trappers have used box traps that corral the raccoon, opossum or occasional stray cat until the trapper returns to kill the fur-bearing animal or release the unwanted one.

http://www.nj.com/opinion/index.ssf/2015/06/keep_those_inhumane_leghold_traps_illegal_in_nj_ed.html