a knotter mechanism , primarily for use in crop baling machines , with an improved billhook and actuation means therefor is disclosed . the billhook is rotatably mounted on the knotter frame and includes a fixed jaw having an elongate shaft and a movable jaw with an integral heel portion is pivotally fixed to the fixed jaw whereby pivotable of the moveable jaw opens and closes the billhook . an actuation means in the form of a rotatable roller is mounted on the knotter frame adjacent the billhook on an axis of rotation perpendicular to the longitudinal axis of the fixed jaw shaft . as the billhook rotates , the heel portion of the moveable jaw periodically engages the roller , resulting in selective opening and closing of the billhook .