This exercise works to widen the lats but this movement will also work other muscles in the back along with the biceps and shoulders.
Grab a pull-up bar with a wide grip. Next, while keeping your torso and straight up pull your body up and try to squeeze your elbows together behind your back as you pull them down. Lean your head slightly forward so that you can touch the bar to the back of your neck. When you get to the top, try to hold your body in this position and squeeze the muscles of your back. Now, lower yourself back to the starting position and repeat for a number of repetitions.
A spotter can be used for this movement, have your spotter hold your legs to lessen the weight that you need to pull. This movement can also be duplicated on a lat pull down machine. The movement should be done exactly the same as prescribed above.