This drill is done in slow motion either at home or on the range, allowing you to feel the proper plane and path of the golf swing.
Start by establishing a fixed position where the ball will sit, perhaps on a tee or a mark on the ground. 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 iron such as a 7-iron for this drill. Trace along the target line to a position one club length toward the target from the ball. From there, move 6 – 8 inches at a right angle toward 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.
Now, go back to the ball and 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, once again 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 two aids which are parallel to your swing plane, one beneath the plane and one above the plane. If our golf swing is on plane, these dowels should not affect anything. Once everything is in place, set up to the ball in your normal set up position. Rehearse in slow-motion a half swing where the club passes underneath the rear dowel and above the forward dowel.
This should give you more of a feeling of approaching the ball from the inside and extending down the target line in your follow through. This drill is well served for beginners or players who tend to slice the ball or come over the top. It is very rare with beginners and higher handicappers, but if you find yourself coming too far from the inside, feel free to reverse the positions of the dowels in order to promote a more outside to in swing path.