“I mean young grown-ups. You’re lucky, you know. You and Jem have the benefit of your father’s age. If your father was thirty you’d find life quite different.”
“I sure would. Atticus can’t do anything...”
“You’d be surprised,” said Miss Maudie. “There’s life in him yet.”
“What can he do?”
“Well, he can make somebody’s will so airtight can’t anybody meddle with it.”
(To Kill a Mockingbird)
I feel like something is missing in the sentence cause there's two verbs(can/can't), and thus having difficulty understanding what this sentence means. If this sentence originally has 'that', I still feel like there has to be a subject. (He can make somebody's will so airtight that ...(?)) Can anyone help me with this?