Many of those checks are gates. They will stop the production line when they find a defect, because they know it's a defect that can reoccur, and won't let a ca

Many of those checks are gates. They will stop the production line when they find a defect, because they know it's a defect that can reoccur, and won't let a car go out with defects. They fix issues on the spot, and immediately incorporate the fixes into the production process. Of course besides gates (Andon cord, kanban) they have other processes: autonomation, poka-yoke, production leveling, kaizen, 6S, etc. But gates keep production in check, and must be efficient, and part of a continuous improvement cycle.