Here is the definition from the SOP: "VULTURE HOCKS: A well defined formation of stiff, straight and rather long feathers growing from the lower part of the lower thighs and projecting backward and downward, a disqualification in all Asiatics including their bantam counterparts; a requirement in d'uccle, Booted, and Sultans."
From the "Bantam Standard", " VULTURE HOCKS: The stiff quill feathers growing in the thighs, extending backward, straight beyond the hocks."
The word STIFF is in both definitions FWIW. There are illustrations of VHs in both standards as well.
Tim