Trolley, trolley. It is the ancestor of all vehicles. Despite the continuous development of material handling technology, handcart is still used as an essential handling tool. Because of its low price, handcart is widely used in production and life. Easy to maintain, easy to operate, light weight, it can work in the place where motor vehicles are not convenient to use, and it is very convenient to transport lighter items in a short distance.
The trolley has one single wheel, two wheels, three wheels and four wheels. Single wheelbarrow can run on narrow gangway, bridge and catwalk. It can be turned to the right place, which is very convenient for dumping goods. The commonly used two wheeled vehicle is a manual carrying vehicle (also known as a tiger car).

Carts and dumpers carrying bulk materials. One of the three wheeled carts has two, four wheeled carts with two rotating casters that can swing around a vertical axis (see rotating casters). This type of caster can automatically adjust to the direction of the minimum driving resistance with the change of the vehicle movement direction during the vehicle operation.