Survival knives are knives intended for survival purposes in a wilderness environment, often in an emergency situation when the user has lost most of his/her main equipment. Military units issue some type of survival knife to pilots in the event their plane may be shot down. Survival knives can be used for trapping, skinning, wood cutting and other uses. 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， Features, such as hollow handles that could be used as storage space for matches or similar small items, began gaining popularity in the 1980s， Custom or semi-custom makers such as Jimmy Lile, Bo Randall, and Chris Reeve are often credited with inventing those features，