Hinge propositions, in Wittgensteins view, are not genuine propositions and are immune to doubt and justification. He spends a good part of the first half of OC discussing them. The denial of a hinge proposition would make the world incomprehensible to us. My so-called study is a jumbled mess. Anyway, Glock argues that hinge propositions are part of the inherited background against which we distinguish between true and false.
Hinge propositions are empirical in that their negation makes sense.
But the possibility of their being false is restricted by the fact that our whole system of beliefs depends on our ready acceptance of them. Doubt concerning them does not fit with anything else we believe. Glock finds four types of hinge propositions, which I will skip. Wittgenstein makes a variety of claims about them. They are certain not just for individuals but for everybody.