A Standard Operating Procedure (SOP) is a written document describing the currently agreed best way to perform a specific task. In lean it is not bureaucracy, it is the baseline against which improvement is measured. Without a standard, there is nothing to improve.
Written by the people who do the work, not by an office. Short enough to be read on the shop floor, usually one or two pages. Structured as important steps, key points and reasons why. Includes visuals: photos, sketches, screenshots. Owned by a named person who is responsible for keeping it current. Reviewed and updated whenever the work is improved.
A standard is not the final word, it is the current best-known method. Its purpose is to make the work repeatable so that variation between operators, shifts and days becomes small. Once variation is small, the process is stable enough to be improved deliberately. Kaizen changes the standard; the new standard is then followed until the next Kaizen.
Standards only produce their benefit when they are actually followed. That requires leader routines: standard work observations, coaching when deviations are seen, and, critically, updating the standard whenever the operator has a better way. If operators see that suggesting improvements leads to real changes in the standard, they follow it and improve it. If not, standards become paperwork.
An SOP is a small, humble document that carries a large idea: the work is important enough to describe, and describing it makes it possible to improve. Every mature lean factory has a living library of SOPs, updated regularly and used every day.
