When mapping some transactional value streams (as well most remanufacturing or maintenance, repair, and overhaul, or MRO value streams), it is possible to quickly get confused about who is the customer and who is the supplier if you try and use the basic mapping technique described in Chapter 13. The concepts of “customer” and “supplier” are fairly straightforward in manufacturing, but the lines begin to blur when you leave basic manufacturing and begin to focus on other value streams.