Vocal overdoers typically have hefty vocal cord muscles and may also have a callus or swelling on the edge of the vibrating portion of the vocal cord. This swelling is typically in the very center of the membranous vocal cord and it stands out from the edge of the vocal cord. This protuberant swelling (or swellings) will touch first as the vocal cords are tensed and leave an opening both anterior and posterior to the swelling. Hence air will leak from in front of and behind the swellings.
This is an extremely common type of gap in vocal overdoers. It is best visualized at higher pitches. As the vocal cords tighten, any marginal swelling is pushed further medially and made more symptomatic and for the examiner, more visible.