Five related terms, beginning with an S sound, describing workplace practices conducive to visual control and lean production. The five terms in Japanese are:
- Seiri: Separate needed from unneeded items—tools, parts materials, paperwork—and discard the unneeded.
- Seiton: Neatly arrange what is left—a place for everything and everything in its place.
- Seiso: Clean and wash.
- Seiketsu: Cleanliness resulting from regular performance of the first three Ss.
- Shitsuke: Discipline, to perform the first four Ss.
The Five Ss often are translated into English as Sort, Straighten, Shine, Standardize, and Sustain. Some lean practitioners add a sixth S for Safety: Establish and practice safety procedures in the workshop and office.
However, Toyota traditionally refers to just Four Ss:
- Sifting (Seiri): Go through everything in the work area, separating and eliminating what isn’t needed.
- Sorting (Seiton): Arrange items that are needed in a neat and easy-to-use manner.
- Sweeping Clean (Seiso): Clean up the work area, equipment, and tools.
- Spic and Span (Seiketsu): The overall cleanliness and order that result from disciplined practice of the first three Ss.
The last S—shitsuke (sustain)—is dropped because it becomes redundant under Toyota’s system of daily, weekly, and monthly audits to check standardized work. Whether four, five, or six Ss are used, the key point to remember is that the effort is systematic and organic to lean production, not a "bolt-on" stand-alone program.