Non-Vocal Primary Top 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.
Non-Vocal Consonant positions have the voice phalanx of the thumb bent at right angles to the breath phalanx, or unaccented. Primary Consonant positions have only the first finger accented. Top Consonant positions have the lower phalanges of the fingers at right angles to the plane of the palm.