I was fascinated when I first saw the picture of Tiger's 8 iron and where the wear mark from the ball was. Of course the precision needed to make a wear mark that small is outstanding. It tells a lot about how good the best players really are. I've added some other photographs I've found on the net. The middle top one is the club of Mike Small, another pro. The others are random golfers I believe.
I've hit some shots with tape on the clubface and I'm hitting it a lot higher than these guys, and all over the face.The lowest dimples show above the second lowest groove, often higher too. You don't need the impact tape shaped like a club face, any thin tape will do. Masking tape works great, and it's cheap.
Here is another good picture.
Mike Bennett hit 17 shots and always placed the ball on the white line. He didn't hit the line once on 17 shots, but still made a nice divot after the ball. This tells us he must have hit the ball low on the clubface while the club was moving down. If you hit it high on the clubface while on the way down, you would start the divot underneath the ball, which would cause loss in distance.
If you hit it that low on the face and the swing bottoms out at the ball, you would hit it thin. It is essential that the club bottoms out 2-4 inches in front of the ball. The shaft must of course lean forward at impact. This is one of the fundamentals to play good golf. If you are able to control the swingpath and face angle too, you're a low handicapper.
This means that you should be able to put a thin towel or cloth right behind the ball and hit the ball without touching the towel. This seems very difficult to those of us who flip or in some other way don't hit the ball with the shaft leaning forward and a forward swing bottom.
I'm a little surprised that I haven't come across a high speed video of the impact from a pro yet, which clearly shows things like this. The videos on Youtube I've seen does not work. The camera needs a lot of FPS, good lighting, sitting at ground level and with flat and closely mown grass.