Long lock bar and short lock bar semi-trailer

2.2 ▣ Long and Short Locking Bars
Long-bar lockbar semi-trailers, the predecessor of the coal transport box semi-trailer, were very popular in the early days, renowned for their fully-opening side doors and long lockbar structure. Long-bar lockbar semi-trailers are suitable for transporting bulk cargo such as coal, while short-bar models are preferred for their lightness and suitability for narrow lanes.
However, with changes in national technical requirements for box semi-trailers and their relatively high curb weight, long-bar lockbar semi-trailers have gradually emerged as a more popular choice. The open roof design of long-bar lockbar semi-trailers allows for easy loading with mechanical equipment. Canvas panels are nailed to the inside of the sides of the lockbar, creating a largely enclosed space, giving them the functionality of a box truck. When the side doors are fully opened, the opening is spacious enough to accommodate forklifts and other construction machinery for unloading. These machines can easily unload cargo, such as coal and sand and gravel, from the box truck, making unloading extremely convenient. Single-bar slab semi-trailers are popular for their compact size and low height from the floor to the top of the slab. Short-bar slab semi-trailers are generally 13 meters long, making them ideal for navigating and parking on narrow roads. Compared to long-bar slab semi-trailers, short-bar models lack a roof rail and have a shorter slab, resulting in a lighter overall weight. Short-bar slab semi-trailers are not only suitable for transporting coal and sand and gravel, but are also widely used in long-distance logistics.