1911 Encyclopædia Britannica/Spring-gun
SPRING-GUN, a device formerly in use against poachers and trespassers. Wires were attached to the trigger of a gun in such a manner that any one stumbling over or treading on them would discharge it and wound himself. Since 1827 spring-guns and all man-traps are illegal in England, except within a house between sunset and sunrise as a protection against burglars. Spring-guns are sometimes used to trap wild animals.