This drill is intended to help players who tend to slice the ball or come over the top. You can hit full shots with this drill, but I would suggest starting with very small swings and progressing to larger swings slowly.
Start by establishing a fixed position where the ball will sit, perhaps on a tee, a mark on the ground, or both. It’s important that the ball’s position does not move once we’ve set up this drill. I suggest teeing the ball up.
Establish a target line by laying a club or dowel in front of the ball and behind the ball pointed in the same direction. Set up a parallel toe line as well, ensuring that your setup will be square and aligned. Use a middle irons such as a 7 or 8-iron.
From the ball, move along the target line 1 club length away from the target. From there, move 6 to 8 inches at a right angle away from your stance side of the target line. At this point, push a shaft or dowel into the ground at an angle parallel to your seven iron in the address position.
If you can imagine the plane of your golf swing, we have effectively set up an aid which is parallel to your intended swing plane, but safely above the plane. If our golf swing is on plane, the dowel should not affect anything, but if we come over the top, we will hit the dowel on the downswing, and receive immediate feedback that the swing was incorrect.
Once everything is in place, set up in your normal position aligned squarely to the target. The club should pass under the dowel in the backswing, then return under the dowel once again in the downswing, impacting the ball from the inside and allowing extension down the target line in the follow-through. I suggest first rehearsing this drill in slow motion to help you get a sense of where the club needs to travel and so you don’t hurt yourself. When you are ready, begin with short 9:00 swings before progressing to anything larger.