Using a squat rack bar lower the bar so that when you are holding it you are almost at a 90 degree angle. Grip the bar with a neutral grip or reverse grip and let your arms be fully extended and your legs straight out weight in your heels.
Slowly begin to pull yourself up by flexing the elbows. Do not use momentum to pull yourself up, the goal is to get the bar to your chest.
Once your chest has reach the bar hold for 1 or 2 counts and slowly lower back down to a full extension.
Repeat for the number of reps.