Trolleys can aid in reducing effort required to move a load by allowing the user to pull or push instead of lift and carry.
Flatbed casters can vary dramatically, made of solid rubber, air filled pneumatic or cast iron.
A U-boat trolley is used to move and stock goods by retailers such as grocery stores, and has two high handles on opposite ends of a narrow flatbed.
Balance trolleys often have wheels mounted on a central axle to create a pivot point, operating in a similar fashion to a seesaw.
The rear axles are fixed to the chassis, and the front wheels are attached to a steering mechanism that allows the trolley to be turned when moved.