Yup, that's what I'm talking about.
I find it interesting that a German speaker would do that. The normal German way of making a relative clause is to use a form of the demonstrative pronoun (roughly like that), unless the relative refers to an indefinite thing or a whole clause, in which case they use the interrogative was. So where we'd say It's something that I've never seen, they'd say something like Es ist etwas, was ich niemals gesehen habe, where was is "what"—"It was something what I've never seen." But when referring to something definite, like "the tools", I was taught to use a demonstrative, which in this case would be die.
But it could be that what I taught is "proper" German, while your father-in-law is using something more colloquial. I don't know German grammar well enough.