If the vocal cords are going from the breathing in, V-shape, toward a parallel position but they stop short of complete closure, this leaves a posterior gap. One example of this type of gap is from muscle tension, where the opening muscles (PCA) partially tighten during phonation competing with the closing muscles (LCA) and hold the cords slightly apart, allowing air to escape between the posterior portion of the vocal cords.
Arrows lie along the direction of closure and point to the gap remaining between the vocal processes when there is incomplete closure.