Casters are collectively referred to as activities and fixed casters. The casters also called the caster, its structure allowed to rotate 360 degrees; fixed casters without rotating structure, can not turn. Usually two casters are used together, such as the structure of the trolley is the front two fixed wheel, behind the push near the handrail is two active caster. Casters in daily life is widely used. Recently, the news of the application of casters in life often see the newspapers, such as a market in front of several large pots are installed under the casters, in order to move the bulky large flower pot; a university in the lanterns at the beginning of the pulley factory gathered on the pulley Family, youth overflowing, free fashion; food street, snack stall to the simple booths on the wheels, back and forth to push, it is convenient; supermarket trolleys, trains, bus stations and logistics push goods Cars, mobile chairs and vendors of carts ... life in the use of casters everywhere ubiquitous. In the life of such a common casters is how to invent it? The history of the casters is long and long, but it is certain that after the wheels are invented, it is easy to move and move the objects, but the wheels can only run on a straight line, and it is still very difficult to change the direction when moving large objects , And later people invented the wheel with a steering structure, that is what we now call the casters or caster. Casters appear to people, especially mobile objects brought epoch-making revolution, not only can be easily handled, but also can move in any direction, greatly improving the efficiency.