Encumbrance is a handy way to limit the amount that a character can carry, but common sense dictates that no matter how large or strong someone is, they only have two hands (usually) with which to carry things. Therefore a bag or some other easily carried storage device is needed to carry more.
Most often made from strong waterproof fabric, a backpack (or knapsack) is worn on the back with a strap for each shoulder.
Similar to a backpack, but slightly larger, sturdier and with various pouches and pockets, rucksacks are often employed by military personnel.
Resembling a large sack with a drawstring and a strap, the sling bag can either be carried in the hand or slung over one shoulder.