The Grenade in a Can was a simple and effective booby trap set by Viet Cong soldiers during the Vietnam War. A primed grenade was put into a container with a string tied around the body. When the grenade is pulled out of the can by force, it will arm and explode, since the pin would be already removed and there would be tension between the handle and the can. This would usually be rigged to a trip wire or an inwards-pulling door.