Understanding Molly Guards: Safety Mechanisms in Computing and Hardware Design

Old-school computing has a term 'molly guard': it's the little plastic safety cover you have to move out of the way before you press some button of significance.

Anecdotally, this is named after Molly, an engineer's daughter who was invited to a datacenter and promptly pressed a big red button, as one would. Then she did it again later the same day.

And some vestigial forms of molly guards exist everywhere in civilian hardware, too.

The reverse molly guard is when you remove the safety, or when the safety is missing, and you're left with a button that's just waiting to be pressed.

In software, we have our own molly guards and reverse molly guards. They're just less obvious.