Golf clubs - equipment

Golf is played with golf clubs of various types. There are four major categories of clubs, known as woods, hybrids, irons, and putters. Wedges resemble irons and may also be counted among these. A golfer is allowed to carry up to fourteen clubs during a round.

While it is possible to play a range of different shots using only one club, modifying only the speed and direction of swing, this is not a particularly successful technique. It is much easier to keep the swing as constant as possible and achieve different lengths and characteristics of ball flight using a different club for each shot. To facilitate the choice of a club for any particular situation, all irons (and many woods and wedges) come in sets of similar clubs graded by loft (see below), shaft length, and weight. Clubs are numbered for identification with the smallest numbers indicating the lower lofts (a 5 iron has less loft than a 6 iron).

Various clubs are designed with the face having differing loft (the angle between a vertical plane and the clubface when the club is at rest). It is loft that makes a golf ball leave the ground on an ascending trajectory, not an upward direction of swing: with the exception of the tee shot, the club actually hits the ball in a horizontal or slightly downward motion. The impact of the clubface compresses the ball. Grooves on the clubface impart a counterclockwise (from a parallel view of the swing) spin, known as backspin, on the ball, that when combined with the rebounding effect of the ball, give it lift. Typically, the greater the loft, the higher and shorter the resulting ball trajectory.

A typical set of clubs generally consisted of 2 woods, 2 wedges, a putter, and 9 irons, numbered 1-9. This has changed greatly in the last 25 years, as most players have opted to take 2, or even as many as 5, of the difficult-to-hit longer irons out of the bag in favor of higher lofted woods, known as fairway woods, and extra "utility" wedges.

Regulations

The ruling authorities of golf, the Royal and Ancient Golf Club of St Andrews (R&A) and the United States Golf Association (USGA) reserve the right to define what shapes and physical characteristics of clubs are permissible in tournament play. Several recently developed woods have a marked "trampoline effect", a large deformation of the face upon impact followed by a quick restoration to original dimensions which acts as a slingshot, resulting in very high ball speeds and great lengths of tee shots. Current USGA and R&A regulations differ with respect to acceptable limits of the "trampoline effect". Therefore, a few club types may not be played in tournament or professional play under USGA jurisdiction, but are allowed elsewhere.

Other large scale USGA rulings involve a 1990 suit, and subsequent settlement, against Karsten Manufacturing, makers of the PING Brand, for their use of square, or U-grooves in their immensely popular Ping Eye2 iron models. The USGA argued that players who used the Eye2 had an unfair advantage in imparting spin on the ball, which helps to stop the ball on the putting greens. Ping ultimately changed the design of subsequent Eye2s, the older clubs were "grandfathered in" and allowed to remain in play as part of the settlement. Today square grooves are considered perfectly legal under the Rules of Golf.