A backpack -LRB- also called rucksack , knapsack , packsack , pack , bookbag or LOCATION@1 -RRB- is , in its simplest form , a cloth sack carried on one 's back and secured with two straps that go over the shoulders , but there can be exceptions .

A backpack -LRB- also called rucksack , knapsack , packsack , pack , Haversack , or LOCATION@1 -RRB- is a cloth sack put on somebody 's back .
