Can I use a non-conforming yardage book or green-reading book in a tournament?

No, you cannot use a yardage book or green-reading material that exceeds the size and scale limits in Rule 4.3a/1. If the Committee adopts Model Local Rule G-12, all green-reading materials are banned. Breach carries a 2-stroke penalty (stroke play) or loss of hole (match play); a second breach means disqualification.

What the rule actually says

Rule 4.3a lets you use equipment for distance and directional information, but you must not use anything that artificially eliminates the need for essential skill or judgment. Interpretation 4.3a/1 specifically limits the size and scale of detailed putting green maps and any similar electronic or digital materials you use during a round to read your line of play on the green. A book that shows contours, slopes, or break in more detail or at a larger scale than the rule allows is non-conforming and prohibited. You can still use a yardage book that gives general distances, hazard locations, and basic green shape — those are treated like any other distance information. The restriction kicks in when the material becomes a detailed green-reading map that does the reading for you.

When the Committee bans everything (Model Local Rule G-12)

A Committee can go further by adopting Model Local Rule G-12. When G-12 is in effect, no player may use any written, electronic, or digital material to help read their line of play on the putting green during the round. That means even a conforming yardage book with green diagrams becomes illegal if it's used for green reading. The Local Rule must be published in the tournament's Terms of Competition or on the notice board; if it's not posted, it's not in force.

Penalties if you get it wrong

First breach of Rule 4.3: general penalty — two strokes in stroke play, loss of hole in match play. Second breach (unrelated to the first): disqualification. The penalty applies per round, so if you use a banned book on the first hole and keep using it, it's still one breach for that round. But if you use it again in a later round of the same competition, that's a second breach and you're DQ'd.

Exceptions that change the answer

• Committee adopts Model Local Rule G-12 → All green-reading materials are prohibited, even those that would otherwise conform to the size/scale limits.
• Material exceeds the size or scale limits in Interpretation 4.3a/1 → It is non-conforming and prohibited regardless of whether G-12 is adopted.

Frequently asked questions

What makes a yardage book "non-conforming" under Rule 4.3?

A yardage book or green-reading material is non-conforming when its putting green maps exceed the size and scale limits set out in Interpretation 4.3a/1 — meaning they show contours, slopes, or break in too much detail or at too large a scale, effectively doing the green reading for you.

What if the Committee doesn't mention G-12 in the tournament rules?

Then G-12 is not in effect. You may use green-reading materials that conform to the 4.3a/1 limits. Always check the Terms of Competition and the notice board before you tee off.

Can I use a yardage book from a previous year's tournament?

Yes, as long as its green maps meet the current 4.3a/1 size/scale limits and G-12 isn't adopted for this event. The age of the book doesn't matter; only its level of detail does.

What's the penalty for using a banned green-reading book?

First breach: two strokes in stroke play or loss of hole in match play. Second breach in the same competition (even a later round): disqualification.