Note the design or layout of the process in a factory. In the past, in this factory every machine out of five of the booth lathes, milling machines, and driller placed side by side: one machine is held by a worker, for example one only holds one turner lathe.

According to the Toyota production system ,The engine layout would be reformed to expedite the flow of production.Therefore, every worker will hold three types of machines. For example, one worker will hold a lathe, a milling machine, and a drilling machine at the same time. This system is called double-handling process (multi-process holding). In other words, single-function workers, a concept that was applicable at the Toyota factory, now a dual-function workers.

In a line of double-handling process, a worker handles several machines from different processes one by one.; Work in each process will take place only if the worker completed the job assigned to him within the specified cycle time. As a result, the entry of each unit into the line offset by the completion of other units of the final product, as ordered by the operation of a time cycle.

Such production is called production and transportation of one piece, it can provide the following benefits:
• Because the product is created one by one, we can shorten the time of production order the product.
• Preparations unnecessary between each process can be removed.
• The concept of dual-process workers to reduce the number of workers required,and thus increase productivity
• As workers become worker-dual function, they can participate in the overall system of a plant and thus feel more comfortable with their work.
• With a dual-function workers, each worker knows how to work together in groups and help each other.

The concept of dual-process workers or employees of such dual-function is a methods that are Japanese. In American and European factories, the division of work too much and there are many trade union skills. As a result of the union workers were paid according to their job class. Because of this agreement, a turner, for example, only handle one lathe and usually will not work on other types of machines. While in Japan, used the system of wages based on seniority and one-union-business for every company, so make the mobility of workers and double-handling process very easy. Clearly, these differences must be addressed by American and European companies that may be interested in using Toyota production system.