Does your driver look like the one in our picture? It's telling you that you cut across the ball..
Wooden tee-pegs are of course painted, and impact can see that paint leave a mark on the sole of your club. With narrower- soled irons, that mark can be a useful indicator of toe or heel strikes; but with the wide-soled driver the streak is often long enough show you exactly the path the club was taking through the ball.
The most common paint mark runs at an angle from the centre of the face towards the toe, indicating a slice path. Trace that angle over an upright tee peg and you can see how the mark was caused by an out-to-in path that cuts across the ball at impact. This is the path that causes slice pain for 85% of club players.
How to fix it
#1: Set Up Check
Straightening out those tee streaks starts with address. Make sure the ball is not too far forward; under your lead shoulder is a good guide. From here ask a friend to check your alignment – feet, hips, knees and shoulders should be parallel to each other and parallel to your ball-target line.
#2: Straighten Your Path
Place a soft object, perhaps a headcover, practice ball bag or even a bottle of water, a foot or so behind the ball, with just enough room for the toe of the club to swing back past it. Go ahead and hit the ball. The simple need to avoid the obstacle on the way down will encourage you to attack the ball from the inside, promoting a more neutral path.