While any knife can be a valuable tool in a survival situation, there does exist a category of knives specifically made for wilderness survival. These knives tend to be, but aren't always, fixed-blade knives with full-tang blades usually 6-10 inches in length. Survival knives typically use durable blade steel that holds an edge to stand up to survival-oriented tasks like building shelter, starting fires, and hunting. There are exceptions to every rule, of course, and the survival knife category is wide and growing.