A horse-face gag is a gagging technique, so called because it distorts the gagged person's face so as to make it look something like a horse.
This type of gag was introduced in the story "Bound in Leather" (1950). The illustrations to this story were by Eric Stanton. The text has been attributed to "J. Cross", but this may have been a pseudonym of Stanton's. The relevant part of the story is:
- The woman, at first, I thought was Vicki. Then I decided she wasn't ... though the eyes looked like hers, the lower part of her face was quite different, being very long from nose to chin, with oddly high cheekbones and hollow cheeks. ... [In fact, it was Vicki.] Her mouth was obviously stretched wide open and packed very tightly I couldn't see what was used for packing, since the lower part of her face was completely covered with strips of adhesive tape. It was the pressure of this tape, which had given the mask the hollow cheeks and high cheekbones.
- "I can see why you call it a 'horse-face' gag," I remarked, as he prepared to remove her cloak, "the great length from nose to chin gives her a very horse-jawed look. Must be very uncomfortable to wear, though."
- "Oh I don't know," he grinned. "I don't hear any complaints."