Essentially a mixed-model production method that operates on production lines that manufacture up to a specific quantity of a particular product each day. These lines also must have the ability to produce unlimited variations of that base product on any given day. Take, for instance, a production line dedicated to building manual car transmissions. A flow line for that product might have the capacity to build 30 transmissions per day. It also would be able to produce the appropriate mix of three-, four-, and five-speed transmissions needed to fill specific customer orders every day of the year. Flow lines achieve this precise level of mixed-model production because they are designed to ensure that each product is built within a specified amount of time. Once the total time it takes to build a product is determined, equal slices of that time are allocated for the performance of each operation along the line. This is called Takt time.

In this way, each product moves through the production process at a steady rate from beginning to end without stopping. When executed properly, this single-unit manufacturing style enables product to move smoothly, precluding the need for excess inventory and preventing unnecessary queues and bottlenecks from forming on the shop floor. This syncopated movement of the product between workstations, must be maintained so that the total time to build a product stays within the limits necessary for all product to be delivered on time