In things like the phalanx formation, how many rows deep would the line be considered a thick line?

Question

Hi, I'm need to know this to do something. If, i am not mistaken, I believed that 3 is considered sufficient. However, what I am talking about is a very thick line. Is it 4, 5, 7, or higher?

Answer 1

From what I could find the Phalanx formation varied anywhere between 8 to 16 ranks deep.