By Guy Yocom June 2008

When the Golf Digest U.S. Open Challenge is played at Torrey Pines on the eve of the U.S. Open, we'll see a test that is perfect in scale. A 10-handicapper trying to break 100 at Torrey, in front of a gallery, national TV audience and three celebrities playing alongside him, would experience a challenge in any case. But with the course in murderously difficult condition, it will be the golf equivalent of climbing Mount Everest without oxygen. His quest will demonstrate how ridiculously hard a U.S. Open course really is, in a language we can understand. Unlike players at other skill levels, a 10-handicapper tends to follow a consistent form and can readily be profiled. Here are some glimpses into what's behind a 10 -- what type of player you can expect, and how he stacks up against everyone else.

WHAT IS A HANDICAP, AND WHY HAVE ONE?
A handicap is a measure of a golfer's potential ability compared to an expert amateur's ability. Getting a handicap will help make your matches fair by eliminating the guesswork in the allocation of strokes for players of varying abilities. Posting your results consistently will also help you track your scoring trends.

HOW IS YOUR NUMBER COMPUTED
? A player actually has two numbers: the Handicap Index and the Course Handicap.The Handicap Index is arrived at by plugging in raw scores and computing them using a formula involving, among other things, the USGA Course Rating and Slope Rating of the course where the round was played.

The Course Rating is a numerical depiction of how difficult a course is for a 0-handicap (scratch) player. The USGA defines the male 0-handicapper as someone who drives the ball at least 250 yards and can reach a 470-yard hole in two shots.

A Course Rating is determined by the cumulative length of holes, and the difficulty of obvious obstacles such as sand and water. When a 10-handicapper describes a course as "a tough test," he generally is referring to a layout with a Course Rating of 72.0 or higher. On a course with a 72.0 rating, a 10-handicapper will score, on average, 82 to 88.

Slope Rating, which the USGA instituted in 1984, is an analysis of the relative difficulty of a course for a bogey golfer when compared to the scratch golfer. Instead of placing an emphasis on the sheer length of a course and obvious obstacles, Slope considers factors that affect the bogey golfer more dramatically than the scratch player. They include topographical features such as hitting to elevated greens; the width of the fairways, trees, water and bunkers that more frequently come into play for the weaker player; the size and contours of greens; and so on. Though a scratch player might consider these factors just a nuisance, they can be significant for the bogey golfer.

Poorer players' scores rise exponentially when playing courses with a high Slope Rating, so they need their Course Handicap adjusted upward accordingly. Though a 0-handicapper playing a difficult course might not need a handicap adjustment, a 10-handicapper might need a couple of extra strokes (or more) to be competitive.

For the Handicap Index, the low 10 of the last 20 results are selected, and the rest are thrown out.

Why not use all 20? Because handicaps are intended to define the golfer's potential. If all 20 scores were considered, the scores shot on bad days would make any player's handicap inordinately high and give a huge advantage if he were to have a good day. This is particularly true among high-handicappers, whose erratic play produces many high scores that would inflate the handicap.

The average of the low 10 numbers is adjusted and is expressed to the nearest decimal point. The 10-handicapper generally carries an Index between 9.5 and 10.4.

The Course Handicap is the whole number the golfer plays with in weekend matches or formal competition. You get that number by matching your Handicap Index against a chart tacked on a wall at the course you're playing (right).

Two key points: Players are expected to make the best score they can at every hole in every round, regardless of where the round is played, and players should post every acceptable round for peer review.

The USGA stipulates that golfers are required to post scores whenever they play at least seven holes. If seven to 12 holes are played, that score is posted as a nine-hole round. If 13 or more holes are played, the score should be posted as an 18-hole round. If you've completed only 13 holes of an 18-hole round, you can still post an 18-hole score. In the case of a 10-handicapper, you would write in pars for unfinished holes with handicaps 11-18, and bogeys on holes where the handicap is 1-10.