Twenty years ago, I was introduced to a graphical method for, as it was put to me, “sharing what you see” with others. It was referred to as a material and information flow diagram, or M&I for short.

Brian S., a consultant from TSSC who was assisting my factory, pointed to a diagram he had sketched earlier in the day and said, “This is how we see the current condition of line X, and I’d like to confirm it with you before we proceed.” I gazed at the drawing, a little reminiscent of a process map, but with symbols like striped arrows and starbursts, and in particular, headstones.

“Headstones!” I exclaimed to Brian. “What do they represent?”

“Stagnation—of either material or information,” he replied. “Like stagnant water: not flowing, smelly, a bad thing.” He pointed to a process box labeled Assembly. “See here: There are eight days of queue in front of assembly. That’s stagnation.”

 …