Single-piece ‹ow, or single-part processing, is the ultimate way to manufacture product, because it allows for the least amount of waste in an assembly line or cell. When it is not possible or practical to incorporate single-piece ‹ow for completing a unit or product, batch or o‚-line processing is required. Batch or o‚-line processing will add waste to the line, so the goal is to simulate ‹ow with the main line or cell while using the least amount of inventory to run the batch and o‚-line processes.