Poka-Yoke is Japanese for mistake-proofing. "Poka" means inadvertent mistake and "yoke" means prevent. It is any mechanism that either prevents a mistake or makes the mistake obvious so that it is corrected immediately. Shigeo Shingo, a Toyota Industrial Engineer, is credited with it's inception.

A good example of a poka yoke can be demonstrated by inserting a floppy disk into your computer, upside down. You will note that it can only go in half way. That is due to a tab inside the slide that is pushed aside by the beveled corner of the floppy disk. The squared corner jams against the tab, stopping the error from happening.

Another everyday example is with the 2 prong plug. You have undoubtedly noticed that you can not plug a 2 prong plug into an outlet without orienting the plug so the large prong is aligned with the widest opening in the outlet. This is not strictly to prevent an error. The motor would still work but it is used to ensure the motor is connected to the proper phase - a rather technical point. With computers, it is nearly impossible to plug a wire in incorrectly. Everything is poka-yoked to ensure you do not cross connect wires.

Let's look at the classic Poka-Yoke, the plastic pocket protector. Yes, it is a Poka-Yoke. It prevents the pen from staining the shirt material should an individual forget to retract the ink cartridge. A very simple Poka-Yoke.