What is Backpack?
[[File:Rucksack1.jpg|thumb|right|A backpack]] A '''backpack''' (also called '''rucksack''', '''knapsack''', '''pack,''' '''Haversack''', or '''Bergen''') is a bag put on somebody's back. It usually has two [[strap]]s that go over the [[shoulder]]s. It is used to carry things in it, and it often has many [[pocket]]<nowiki/>s or [[compartment]]s to carry things. People often use backpacks when [[camping]], [[hiking]], or other activity where they need to carry many things. Backpacks are also used in the military by soldiers. When used in school they are called bookbags or school bags. Large backpacks, used to carry loads over 10 kg (22 lbs), and smaller sports backpacks, usually offload the biggest part of their weight onto padded [[hip]] belts. This leaves the shoulder straps mainly for keeping the load in place. This makes it easier to carry heavy loads, because the hips are stronger than the shoulders. It also improves agility and balance, because the load lies closer to the center of [[mass]] of the person wearing it. In the distant past, backpacks were used to carry hunters' larger catches. If the hunts were even larger, the hunters would [[butcher]] their prey into pieces and hand out the pieces to other hunters. The hunters would then carry smaller pieces separately. The bag would be made up of animal skin and sewn together by animal intestines. They would then be woven together tightly to make a firm material. Some backpacks are specialized to carry a particular thing, such as fluids or a [[laptop computer]]. == Designs == Most backpacks can be closed with a buckle, a [[zipper]], or a dry-bag type closure. A backpack may or may not have a pack frame. If it does not, it is frameless. If it has a frame, it may be external or internal. A pack frame supports the pack and scatters its weight across the body. Most of the weight is taken off the shoulders. This way, users are less often injured, and the upper body moves freely. [[File:Frankfurt am Main (DerHexer) 2012-05-11 01.jpg|thumb|188x188