Previously, postal code was required for mailing letters. It uses the name and address positioning tool of Standard Arabic numerals in a fixed position to realize the automatic sorting of postal services, promote the modern postal services, and improve the sorting processing efficiency and overall transmission speed of letters by more than 10 times. However, in recent years, letters and small express are no longer required to fill in the postal code, instead of the mailing address and recipient's mobile phone number, but the delivery speed is much faster than the original postal code mode.

      The implicit logic of this change is the popularization and application of QR code. Letters and small-size express parcels further improve the sorting processing and system delivery speed of small and medium-sized express parcels through QR code waybills and automatic sorting equipment, as well as the cloud service platform that accurately connects users and couriers. "Next day delivery", "same day delivery" and even "hour delivery" in the same city have become the most common service modes in the express market.

      Container, which is widely used in international logistics and freight transportation, is one of the greatest inventions in the 20th century. Although the container is only a simple standard loading box, Malcolm & middot, the head of the truck enterprise; Under the transformation of McLean, it has become a complete set of cargo handling system including ports, ships, cranes, storage equipment, trucks, railway vehicles and operators. In particular, under the modeling and optimization of Professor Weldon of Johns Hopkins University, it has formed the most economic size of 20 foot unit container, which has triggered a revolution in the shipping industry.

      Nowadays, container plays an irreplaceable role in international trade and world economy. It has created a highly automated, low-cost and low complexity cargo transportation system, which not only reduces the transportation cost, but also shortens the transportation and storage time, and lays a technical foundation for the efficient connection and system operation of rail, sea, land and air multimodal transport.

      Pallet and reel transportation is another horizontal platform device with standard load goods and products, which is used in container loading, stacking, handling and transportation, so as to realize the unitization, standardization and standardization of article packaging. It is not only conducive to the protection of goods, but also can meet the needs of orderly flow of logistics and business flow with high efficiency and low cost.

      However, with the trend of smaller volume, lighter weight and higher value of commodity goods, as well as the efficient connection trend of "door-to-door" between transportation / storage and end distribution, the open pallet transportation mode is becoming more and more limited. Forklift is the main loading and unloading tool, which is also easy to damage the pallet, resulting in the conflict of interests between upstream and downstream parties in the supply chain and affecting the promotion of reel transportation.

      Therefore, the intelligent logistics operation platform supported by information technology needs to select the smallest closed loading unit that is always applicable to the "last kilometer" distribution and form standardization. This standardized minimum closed loading unit not only has the optimal space utilization that can be accommodated by traditional containers, but also can meet the optimal size constraints of "door-to-door" transportation. It also needs to have more efficient, faster and safer automatic loading, unloading and sorting facilities.

      The new closed loading unit should fundamentally meet the "door-to-door" whole process closed without replacement, which can not only efficiently sort at the logistics node, but also close and exchange at the connection of various transportation modes. In 2016, the author proposed the "LEGO" type foldable combination sub container in the container, that is, 2 & times in a 10 foot container; 3× 3 or 2 & times; 2× 3. Minimum enclosed loading / holding unit with size of 1200mm & times; 1000mm× 1200mm or 1200mm & times; 1000mm× 1450mm, similar to the box of Jingdong distribution trolley at present.

      "Standard container standard combination sub container" can become a cost tool and efficiency tool for "door-to-door" logistics market competition, which is enough to replace the open standard pallet with awkward positioning and difficult market operation among logistics nodes.

      Smart logistics will realize the standardization and scale of larger items that are difficult to be standardized in the past at low cost and high efficiency, and the optimal size closed loading unit will also promote the intelligent improvement of the logistics system.