Seiketsu is the fourth S of the series of five and comes logically after Sorting out, Set in order and Sweeping. The first three S reset an environment suitable for safe and efficient work, the fourth S then sets standards so to keep these good condition and practices in the work area.
Without appropriate standard the situation would slip right back and old habits would return.
Seiketsu aims to maintain high standards of housekeeping and workplace organization at all times, by everybody. Standard should also be understood as a set of rules defined for harmonious living / working together.
Standards must make deviations visible, that’s why visual management is often used. If all tools must be return to the tool board by the end of the day, a shadow board will make it easier to spot the missing tools.
The equivalent exists in office: in order to ensure using the up-to-date documents, only one controlled copy is allowed in the office. These documents are shared and must be returned to the shelf immediately after use. The slant line across files helps to see the missing or misplaced files from distance.
The daily cleaning of the workplace by people themselves is a matter of respect to themselves, to their colleagues, a way to keep the place tidy and orderly. But daily cleaning of a machine is also a way to inspect it (see this post for more details).
The daily cleaning as well as the 5S standards at large are usually associated to industrial hygiene.
Standardizing can be about using only one single tool for all adjustments, which needs all tightenings being unified.
These rules are defined by the stakeholders themselves within certain limits such as safety, security rules, quality or any regulatory or formal standards.
Giving the opportunity to stakeholders to define their standard helps overcome resistance to change and fosters commitment to these self-edicted rules.
Standards are meant to be revised, better rules, better standards may surface after certain time. Seiketsu is by no means freezing one standard, but encouraging improvement to better, higher standards.