Containers

Containers hold cargo in standardised specifications that streamline shipping operations based on the intermodal nature.

Sizes that fit on ships, rail, and trucks.

The International Maritime Organization (IMO) published a set of shipping container standards in the 1970s. Standard shipping containers are 8' wide by 8'6" high, while high-cube units measure 9'6" high; about 90% of the world's containers are 20 feet or 40 feet long

https://www.iso.org/iso-in-figures.html

These standards were created by the International Organization for Standardization, the independent, non-governmental body responsible for establishing standards in information technology, graphics, photography, mechanical engineering, transport, non-metallic materials, health, medicine, and laboratory equipment.

Four years ago, they released a set of standards designed to include considerations for ships over 18000 TEU, a direct successor of the original framework. During the late mid-century era, though, the common container was 20'L x 8'W x 8'6"H, which is known as the “20-foot equivalent unit” or TEU, the standardized measurement unit of global trade today.

https://www.iso.org/ics/55.180.10/x/

How were such standards enforced? Initially, they were held up by incentive: Only ships that were built to carry standard sizes were eligible for federal subsidies. Later, the ISO standardized container corner fittings, too, which made it possible to standardize the cranes and other equipment required for moving containers.