A putter is a club used in the sport of golf to make relatively short and low-speed strokes with the intention of rolling the ball into the hole from a short distance away. It is differentiated from the other clubs (typically irons and woods) by a clubhead with a very flat, low-profile, low-loft striking face, and by other features which are only allowed on putters, such as bent shafts, non-circular grips, and positional guides.
Putters are generally used from very close distances to the cup, generally on the putting green, though certain courses have fringes and roughs near the green which are also suitable for putting. While no club in a player's bag is absolutely indispensable nor required to be carried by strict rules, the putter comes closest. It is a highly specialized tool for a specific job, and virtually no golfer is without one.
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Putting is the most precise aspect of the game of golf. The putter must be designed to give the golfer every technical advantage including smooth stroke, good glide, sweet impact, and bounce-less topspin ball launch as well as every technique advantage including perfect fit as to shaft angle and length.
The striking face of a putter is usually not perpendicular to the ground: putters have a small amount of loft, intended to "lift" the ball out of any depression it has made or settled into on the green, which reduces bouncing. This loft is typically 5-6°, and by strict rules cannot be more than 10°. The putter is the only club that may have a grip that is not perfectly round; "shield"-like cross-sections with a flat top and curved underside are most common. The putter is also the only club allowed to have a bent shaft; often, club-makers will attach the shaft to the club-head on the near edge for visibility, but to increase stability, the shaft is bent near the clubhead mounting so that its lie and the resulting clubhead position places the line of the straight part of the shaft at the sweet spot of the subhead, where the ball should be for the best putt. This increases accuracy as the golfer can direct their swing through the ball, without feeling like they are slightly behind it. Many putters also have an offset hosel, which places the shaft of the club in line with the center of the ball at impact, again to improve stability and feel as, combined with the vertical bend, the shaft will point directly into the center of the ball at impact.
The design of the putter's club head has undergone radical change in the last 20-30 years, as have many club types. The putter was originally a forged iron piece very similar in shape to the irons of the day. Through attempts to lower the center of gravity of the club head, it evolved into a shorter, thicker head slightly curved from front to rear (the so-called "hot dog" putter). The introduction of investment casting for club heads allowed drastically different shapes to be made far more easily and cheaply than with forging, resulting in several design improvements. First of all, the majority of mass behind the clubface was placed as low as possible, resulting in an L-shaped side profile with a thin, flat club face and another thin block along the bottom of the club behind the face. Additionally, peripheral weighting, or the placing of mass as far away from the center of the clubface as possible, increases the moment of inertia of the club head, reducing twisting if the club contacts the ball slightly off-center and thus giving the club a larger "sweet spot" with which to contact the ball. Newer innovations include replacing the metal at the "sweet spot" with a softer metal or polymer compound that will give and rebound at impact, which increases the peak impulse (force x time) imparted to the ball for better distance. Putters are subdivided into mallet, peripheral weighted and blade styles. Power instability and practice/play convertibility are features embodied in the latest putter design technology.
Though most putters have a 32 in (81 cm) to 35 in (89 cm) shaft (slightly shorter for most ladies and juniors, longer for most men), putters are also made with longer shaft lengths and grips, and are designed to reduce the "degrees of freedom" allowed a player when he or she putts. Simply, the more joints that can easily bend or twist during the putting motion, the more degrees of freedom a player has when putting, which gives more flexibility and feel but can result in more inconsistent putts. With a normal putter, the player has six degrees of freedom: hands, wrists, elbows, shoulders, waist and knees, all of which can be moved just slightly to affect the path of the ball and likely prevent a putt from falling in the cup. Such motions, especially nervous uncontrollable motions, are called "yips", and having a chronic case of the "yips" can ruin a golfer's short game. German professional golfer Bernhard Langer is famous for having such a severe case that he once needed four putts to hole out from within three feet of the cup.
A belly putter is typically about 6 in (15 cm) to 8 in (20 cm) longer than a normal putter and is designed to be "anchored" against the abdomen of the player. This design reduces or removes the importance of the hands, wrists, elbows, and shoulders. A long putter is even longer and is designed to be anchored from the chest or even the chin and similarly reduces the impact of the hands, wrists, elbows and shoulders. The disadvantages are decreased feel and control over putting power, especially with the long putter. Their use in professional tournaments is hotly contested; Jim Furyk and others on the pro tours including Langer and Vijay Singh have used belly putters at some point with a marked improvement of their short game, while players like Tiger Woods and officials like former USGA technical director Frank Thomas have condemned it as conferring an unfair advantage on users.
In November 2012, a proposed change for the 2016 edition of the rules of golf was announced, which would forbid players from anchoring a club against their body in any way. This rule change will affect the use of long and belly putters by players. Notable players affected include Adam Scott, Tim Clark, Kevin Stadler, Keegan Bradley, Webb Simpson, Carl Pettersson and Ernie Els. This new rule (14-1b Anchoring the Club) was approved in May 2013 and took effect on January 1, 2016. This new rule prohibits "anchoring" a putter when making a stroke. It does not ban long-shafted putters, rather, it bans the method by which they were originally designed to be used.
As putting is one of the most important aspects of a player's golf game, a variety of teaching tools and trainers exist to assist the player in learning correct technique. Though many tools are simply simulations of a putting green such as indoor putting mats and cups, or attachments such as laser guides, some tools are integral features of a "training club". One such tool is the breakaway; a hinged joint in the shaft of an otherwise normal putter that stays rigid until a certain amount of force is applied, then gives way. This is used to teach golfers to use a steady, even putting motion without any sudden pressure applied by the hands or arms to swing the club, creating a more relaxed, controllable putt. Another feature is a curved face, sometimes severely so. Though most putter faces are flat and, depending on other aspects of the head design, very forgiving, the curved putter face forces the player to contact the ball with the very center of the clubfeet in order to hit a straight shot. All other shots will carom off in odd directions or will curve off the intended putting line. Other training clubs incorporate very lightweight heads which encourage a firmer upper body posture that reduces wrist and arm movement, or to the opposite extreme a very heavyweight head that encourages the user to adopt the "pendulum swing" technique and use the weight of the club instead of muscle power. Almost all of these can be used as a "real" putter, but the idea of these devices is to make putting harder than with a real putter as the desired result only occurs when the player utilizes perfect technique, and therefore they are normally used only in practice environments.