The couplet is a popular poetic device. A couplet contains two lines of verse that usually rhyme, though this isn't required. The lines can be any length and use any rhythm. Sometimes the two lines are the same length, and sometimes one is longer than the other. Couplets are often used to end a stanza, but they can also constitute the whole poem.
It travels through the carpal tunnel which is the point connecting the palm and forearm, and goes into the thumb. This muscle is located between the two muscles which facilitate flexion of the thumb, namely the Flexor Pollicis Brevis and the Abductor Pollicis. Flexor Pollicis Longus terminates at the tip of the thumb.
Medical Definition of abductor pollicis brevis. : a thin flat muscle of the hand that abducts the thumb at right angles to the plane of the palm.