Poka-yoke

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Poka-yoke (ポカヨケ - pronounced "POH-kah YOH-keh" means "fail-safing" or "mistake-proofing" — avoiding (yokeru) inadvertent errors (poka)) is a behavior-shaping constraint, or a method of preventing errors by putting limits on how an operation can be performed in order to force the correct completion of the operation. The concept was originated by Shigeo Shingo as part of the Toyota Production System. Originally described as Baka-yoke, but as this means "idiot-proofing" the name was changed to the milder Poka-yoke. One example is the inability to remove a car key from the ignition switch of an automobile if the automatic transmission is not first put in the "Park" position, so that the driver cannot leave the car in an unsafe parking condition where the wheels are not locked against movement. Another example can be found in a normal 3.5" floppy disk: the top-right corner is shaped in a certain way so that the disk cannot be inserted upside-down.

[edit] References

Shingo, Shigeo. Zero quality control: source inspection and the poka-yoke system. trans. A.P. Dillion. Portland, Oregon: Productivity Press.1986.
Nikkan Kogyo Shimbun, Ltd.: Poka-Yoke: Improving Product Quality By Preventing Defects Productivity Press, 1987 (Japanese), 1988 (English), ISBN 0-915299-31-3.
Hinckley, C.M. and Barkan, P. 1995. The role of variation, mistakes, and complexity in producing nonconformities. Journal of Quality Technology 27(3):242-249.