There are also single-strap packs that are essentially a hybrid between a backpack and a messenger bag.
Inexpensive, very simple packs that combine the drawstring and straps into a single piece of cloth or webbing are occasionally sold for use at sporting events and the like. Some high-end retailers (notably Apple Stores) use a similar design for their shopping bags as well.
Rolling backpacks are backpacks with wheels on the bottom and an extending handle to ease carrying objects inside the backpacks. Because of its design, rolling backpacks reduce the strain on one’s back, which is more ergonomic than regular backpacks, though some rolling backpacks can be carried on the back as well. Rolling backpacks are most commonly used to carry extensive amounts of items or moderately to very heavy items in places such as airports and international/transstate train stations.