The Andon Cord is a rope, when pulled, would instantly stop all work on the assembly line. Anyone is obligated to pull the cord at any time if they discover a problem
Once all production is halted, a team leader has to immediately go ask why the rope was pulled. Then, together, the leader and the team could work to solve the problem and restart production.
The Andon Cord is an abrupt (and effective) way of dealing with manufacturing issues at the source, before they fester into something much worse.