Answer: knuckles

AnswerCrossword Clue
KNUCKLESSandwich filler
knucklesA part of a finger at a joint where the bone is near the surface, esp. where the finger joins the hand
knucklesA cut of meat consisting of such a projection together with the adjoining parts
knucklesA projection of the carpal or tarsal joint of a quadruped
knucklesKNUCKLE, to hit with the joints of the fist