Actually, that isn't completely true. There is also "A Convention for Proposing Amendments...as Part of This Constitution".
We know, of course, that the "living Constitution" school has ignored the provisions of the document itself.
At a seminar some years ago, I heard a constitutional law professor respond to a question about amending the constitution by praising the role of the courts and judicial activists in bringing about changes, saying, "We've had what amounts to a 'sitting' convention."
That's not what the Founders intended as we know.