
23Introduction to Lean
other waste. The rocks represent waste that was “hidden” by either inventory or other wastes or
“work arounds” created within a process, otherwise known as “hidden wastes.” As one lowers the
water (inventory), which in healthcare can be reducing patients waiting times, overowing charts,
or excess operating room (OR) or hall supplies and instrument sets surface, one starts to expose the
problems or rocks (other hidden wastes) underneath along with all the variations that exist in the
system. One must make sure there is a continual pursuit to drive down waste.
JIT does not mean zero inventories. All systems need some in