This was part of the Japanese manufacturing craze a few years back, but it is definitely worth keeping some of the principles in mind when designing anything. It basically translates as “idiot-proofing”.

Essentially you need to consider what someone could do wrong at every stage of manufacture, installation and use, and try to prevent it happening by design.

For example, if you are designing two parts which someone is going to have to connect together, ideally it shouldn’t matter which orientation they are in. Failing that, they should only fit together one way.

If you have two connectors to plug into a box, ideally it shouldn’t matter which one you plug in where, or failing that the connectors should only physically fit into the right sockets. At the very least you should colour-code the connectors and the corresponding sockets so that it is obvious when they are connected incorrectly.