A knife is a handheld sharp-edged instrument consisting of handle attached to a blade used for cutting. The knife is a tool that can be used as a weapon. Survival knives are intended for survival purposes when lost in a wilderness environment. Military units issue some type of survival knife to pilots in the event they may be shot down. Hunters, hikers, and outdoor sport enthusiasts use survival knives. Some survival knives are heavy-bladed and thick; others are lightweight or fold in order to save weight and bulk as part of a larger survival kit. Their functions often include serving as a hunting knife.