The Square Club Face
If an open club face sends the ball slicing (curving) to the right of the target line, and a closed club face sends the ball hooking (curving) to the left of the target line, then a square club face will send the ball along the target line. This is assuming, of course, that your swing is on path, that you are lined up properly, and that the basic swing motion has engaged all the parts of the body with the right timing.
If, when you address the ball, the club face is square to the target line and the knuckles of your forefinger and pinkie on your left hand are also square to the target line, then the properly executed swing will return the club face and the knuckles to that setup position, and the ball will fly true to course.
If you have to make adjustments to the angle of the club face at setup in order to hit the ball straight, something's wrong with your swing. The ball may go straight after the adjustment, but you'll never be able to hit is as accurately, as far, or with the right spin.