Nick is the repair Mr. Handy. The state of the vault may give you a glimpse into how dedicated Nick has been about his job. While he's more than happy to shoot the shit, when things need to be fixed he always has some reason why it can't be done right now. Need a new part. Or his optical input needs adjusting. There's a thousand reasons. It takes a strong hand to get Nick to do much of anything, much to the annoyance of the other Mr. Handy's in the vault. He can be mostly found in the reactor level, not that it does much good.