Square to Square (STS)
In this stroke the putter travels straight back and straight through on the target line. The face of the putter is always pointed at the target during this stroke. This style of putting is used by golfers of all skill levels including PGA tour players, but may be especially helpful for beginners and for practicing short putts.
In this stroke, the putter travels INSIDE the target line on the backstroke, returns to SQUARE at impact, and travels back INSIDE the target line on the follow through. Some instructors believe this stroke to be more natural and resembles a miniature golf swing. During this stroke the face of the putter opens relative to the target line, but remains square to the arc along which it is swinging. Most of the players on the PGA tour use some variety of this method.