Lean Systems Sustain - the Fifth "S" of the 5 S System If you have gone to all the work of setting up the system you must sustain or even improve on it to keep the system working properly. Things change and you need to be flexible.… by Ken November 12, 2009 chat_bubble_outline0 Tags: 5 S's, Efficiency, Lean, Lean Systems, Lean Thinking, Process Improvement, toyota production system