In the university campus scene in Raiders of the Lost Ark, Indy is writing "NEOLITHIC" on a black board. He reaches 'H', but pauses after putting down the two vertical strokes, seemingly confirms something and resumes writing it. What is the meaning of this?
He's reminding himself how to spell the word.
If you listen, he spells the word to himself, trying to remember the correct letters.
"Neo," meaning "new" and "lithic"... L-I-T-H...I-C, meaning "stone."
That's all it is. A minor gag, just the slightly absent-minded professor of archaeology needing to remember how to spell an archaeological word.