Vocalized Primary Back Consonant
Consonants have a closed or narrowly expanded adjustment of the vocal organs, so that in their production some part of the throat or mouth obstructs, squeezes, or divides the breath. …in representing consonants the hand suggests a narrow adjustment of the organs, by having the prominent or accented fingers straightened and the second phalanx of the thumb close to the plane of the palm.
Vocalized Consonant positions have the voice phalanx of the thumb accented; that is, brought in line with the breath phalanx; this constitutes the only difference between the Vocalized and analogous Non-Vocal Consonant positions. Primary Consonant positions have only the first finger accented. Back Consonant positions, being posterior, have the palm held laterally at an angle to the arm.