Place a flat bench (or a box that you can sit on) a few feet away from a cable machine and set a single pulley attachment as high up as you can.
Sit on the bench and extend your arm directly to your side at roughly a 45 degree angle and grab the attachment using an underhand grip.
Tilt your upper body slightly in the direction of the machine and then pull the resistance inward toward your side until you feel a strong contraction in your lats. Raise the cable back up following the same path and repeat.