Square Pull Ups
For the Square Pull Ups, grab the bar with a overhand grip as if you were about to do a pull up. From a dead hang shift your body to the right so that your weight is mostly distributed over your right arm. From that position, pull your chest up to the bar. Once at the top, shift your body across the bar so that your chest is distributed under your left arm on the bar. From there drop your body down and return to the starting position. The range of motion should have your torso moving in the shape of a square.
This exercise uses the same muscles as in a pull up, but puts more strain on each side individually. It is a great way strengthen the lats shoulders and flexor muscles of the arm individually, and is a great progression to learn the single-arm pull up.