I found another reason that the line is helpful. I don't use the line after reading some of David Orr's posts on how the line doesn't help golfers that much and it is tough sometimes to get it aligned the way you want to. However, I just got a putter fitting Monday and we reduced my skid by about 20%. Now I have a new putter and it's reduced by greater than 25%. Before with the old putter if I putted on the line the ball would inconsistently roll end over end. Now with an improvement on the putter, my ball rolls very consistently end over end. I have been trying it out on the practice green. So if you have questions about your skid, using the line may give you a decent answer.