Poka yoke is a Japanese term meaning inadvertent error prevention and was developed by Toyota. It is aimed at stopping errors at the point that they are occurring. Most mistakes are accidental and are caused by various factors such as overly complicated procedures, inadequate training or a loss of concentration.
A simple example is a British 3 pin plug. It cannot be inserted incorrectly and the earth pin is longer so it is the first contact with the socket.
The Poka Yoke Process