Spec Primer

Lie angle

The angle between the shaft and the ground when the club is soled. It is measured in degrees and described relative to a manufacturer's standard, so "two flat" means two degrees flatter than whatever that maker calls standard — and standards differ by up to three degrees between brands. This is why comparing lie numbers across makers is meaningless without also knowing the baseline.

Lie matters because it points the leading edge. Too upright and the leading edge aims left of the face; too flat and it aims right. For a short iron, one degree of lie error moves the ball roughly three to four yards offline at 150 yards. On a wedge, more.

Playing length

Measured from the butt of the grip to the ground along the sole line, with the club in playing position. Not the same as raw shaft length, and not the same as the number printed on a box. Playing length interacts with lie: add half an inch and the club plays roughly a degree more upright unless the lie is corrected to match.

Loft

The angle of the face relative to vertical. Iron lofts have strengthened substantially over the past two decades, which is why a modern seven iron can carry as far as an older six. The number is useful within a set for checking gapping and useless for comparing between sets.

Swingweight

A letter-and-number scale (C8, D2, D4) describing how head-heavy a club feels when swung. It is a ratio measurement, not a mass measurement: a heavier club can have a lower swingweight than a lighter one. Roughly, half an inch of length equals three swingweight points, and two grams of head mass equals one point. This is the specification that gets destroyed when a club is cut down without compensation.

Total mass

What the whole club weighs on a scale, in grams. Swingweight tells you about balance; total mass tells you about effort. Two clubs at identical swingweight can feel entirely different if one is forty grams heavier overall, and for players managing fatigue or joint pain, total mass is usually the more important of the two.

Shaft weight and flex

Weight in grams is a real measurement and worth paying attention to. Flex letters — L, A, R, S, X — are not standardised at all. One maker's regular is another's stiff, and the same letter varies within a single maker's range. On a build sheet we record the shaft model, its weight, and its measured frequency where relevant, because those numbers travel between brands and the letter does not.

Tip trim

How much material was removed from the narrow end of the shaft before installation. Tip trimming stiffens the lower section of a shaft and lowers ball flight. A shaft trimmed to different specifications is genuinely a different shaft in play, which is why the sheet records it. It also means two clubs with the same model name printed on them are not necessarily comparable.

Grip core size and tape build

Grips come with a core diameter (typically .580 or .600 inch) that must match the butt diameter of the shaft. Beyond that, additional layers of tape build the grip up in known increments — roughly one thirty-second of an inch per four wraps under the lower hand. Build-up affects hand pressure and forearm rotation, and for players with arthritis it is frequently the single most useful change we make.

Bounce and grind

Bounce is the angle between the leading edge and the lowest point of the sole. Grind describes how material has been removed from the sole to change how that bounce presents when the face is opened or the shaft is leaned. The stamped bounce number describes a club sitting square and level; what you actually play is the effective bounce at your delivery, which can differ by six degrees or more.

Offset

How far the leading edge sits behind the hosel. More offset gives the hands a fractionally longer moment to square the face and visually frames the ball differently at address. It also changes how the club sits, which is why a set with progressive offset can read differently on the board from the long irons to the short ones.