A litter is a stretcher or basket designed to be used where there are obstacles to movement or other hazards: for example, in confined spaces, on slopes, in wooded terrain. Typically it is shaped to accommodate an adult in a face up position and it is used in search and rescue operations. The person is strapped into the basket, making safe evacuation possible. The person generally is further protected by a back board and a cervical collar, so as to immobilize the person and prevent further injury. A Stokes basket, also called a Stokes stretcher or Stokes litter, is a metal wire or plastic litter widely used in search and rescue.[1] Its key feature is that it can be disassembled for transport in backpacks or by pack horse.[citation needed] Originally designed by Charles Francis Stokes,[2][3][4][5][6] these baskets have been notorious for spinning under the downdraft from the rotating helicopter blades.[citation needed] Design improvements have included using multiple attach points, separate hold-down cables, and powered extension hoists to help save more lives. Recently the U.S. Navy has used the Stokes to transport patients through narrow corridors and doorways. Keep in mind that Class 1 through Class 4 rankings are not very descriptive and do not have any further breakdowns like Class 5. Class 2 is very general and includes a wide range of hiking. At times, Class 2 routes may include dangerous terrain (exposure, loose rock, steep scree, etc.). Just because a route is ranked Class 2, does not mean it is safe or easy. The key to Class 3 is that you are almost always using your hands to move up through the steep terrain (snow or rock). In some cases, I may describe a route as “Difficult Class 2”, or “Easy Class 3” to provide more detail.