device

an instrumentality invented for a particular purpose; "the device is small enough to wear on your wrist"; "a device intended to conserve water"

something in an artistic work designed to achieve a particular effect

any clever maneuver; "he would stoop to any device to win a point"; "it was a great sales gimmick"; "a cheap promotions gimmick for greedy businessmen"

any ornamental pattern or design (as in embroidery)

an emblematic design (especially in heraldry); "he was recognized by the device on his shield"