For many golfers who cut across the ball and have tendencies to slice or shank the golf ball the problem is most likely to be focused around the downswing and release. 

Metcalfe believes that one of the problems golfers tend to have is that they don't release the club correctly and they will move their hands too quickly towards the ball causing them to get above plane and slice or shank their shots. 

Therefore, by focusing on this simple drill of a better downswing with a lead arm release, the will naturally swing on an arc which will lead to sucessful and more consistent golf shots.