The Chicago Manual of Style (CMOS) uses a 5-level heading system. In engineering, this is vital for nested data (e.g., a sub-section of an experiment within a larger chapter).
Level 1: Centered, Boldface or Italic, Title Case.
Level 2: Centered, Regular Type, Title Case.
Level 3: Flush Left, Boldface or Italic, Title Case.
Level 4: Flush Left, Roman Type, Sentence Case.
Level 5: Run-in at beginning of paragraph (bold or italic), followed by a period.
Pro Tip: Do not end a page with a heading. If a heading falls at the bottom of a page, move it to the top of the next page so the text follows immediately.