Toyota Firewall Tool
This Firewall tools also known as QA Matrix (QAM) one of Toyota approach. Apparently this approach to ensure there's no defect product delivered out to customer by doing station by station filter. Every station will filter the defect and from that we can evaluate the checkpoint or station efficiency until at the end (green level).
Red - "Station with no detection"
Yellow - "Station with no 100% coverage"
Green - "Station with 100% coverage"
Currently my company is still in-progress of implementing the tools upon our customer, Blaupunkt(BOSCH) requirement for their product.