A heretics fork was an instrument of torture, attributed to the Spanish Inquisition and designe dto make a suspected heretic confess.
it consisted of a bar with two sharp prongs at each end, which was fastened tightly by a collar to the victim's throat. This made the prongs press against his chin and sternum; he was forced to hold his head back and motionless to avoid having the prongs pierce him; after a while, this caused agonising cramps in his neck. He would probably have had difficulty in speaking. The fork was supposed to be engraved with the word "abiuo" ("I recant"); the wearer was told that he had to say this word.