It's a small spiral-bound book — fits in your back pocket — with a detailed diagram of every hole on the course. Not just yardages from the tee. Everything: distances to bunkers, water, trees, false fronts, and landing areas. Detailed green maps showing slopes, tiers, and where putts break.

The good ones are built from laser surveys and on-the-ground walks by someone who has charted every inch of the course. A college player pulling one out before a shot isn't stalling — they're confirming a number they already have in their head, cross-referencing the green contour they marked during the practice round, and committing to a shot they've already decided on.

That's the key word: confirming. A yardage book is not a decision-making tool. It's a confirmation tool. If your junior is standing over the ball calculating instead of committing, the book is slowing them down, not helping them.

Not for their home course. Not for a Saturday round. Not for their first ten tournaments.

A yardage book starts to earn its place when:

• Your junior is playing a course they've never seen before.
• The event is a qualifier or invitational where course management actually affects the result.
• They're old enough and experienced enough to use it without slowing down.
• They have a practice round to walk the course and mark it up.

For most juniors under 14, a yardage book is more distraction than tool. At that stage, fundamentals and course feel matter more than precise distance confirmation. A GPS watch or rangefinder (where allowed) does the job at that level.

At the AJGA invitational level and above, a yardage book is standard. The field will have them. Your junior should too.

• StrackaLine — the most widely used source for junior tournament courses. Detailed green books with slope and contour information. Available online before most events.
• GolfLogix — another solid source, good coverage of tournament courses across the country.
• The host club pro shop — often overlooked. Many clubs sell their own yardage book in the pro shop for $15–25. Sometimes these are the most detailed because they were made specifically for that course. Ask when you arrive.
• Tour-level books — companies like Mark Long and GolfBook produce the books used by PGA Tour players. Extremely detailed, expensive, and more than most junior tournaments require. Worth knowing they exist as your junior moves up.
• If you can't find a commercial book for the course, your junior can build a rough version during the practice round — diagram each green, note key distances, mark where the trouble is. It won't be laser-surveyed but it's better than nothing.

The practice round is when you mark the book. Not during the tournament.

During the practice round, your junior walks each hole with the book open — noting which bunkers are actually in play, where the false fronts are, where putts break, which pin positions are trouble. They write in the margins, circle numbers, draw arrows on the green maps. The book becomes a record of what they learned.

During the tournament, the book confirms what they already know. The pre-shot routine already includes the yardage — the book is the last check, not the first thought.

On the green specifically: use the green book after everyone in the group has hit their approach and is walking to the green. Don't stand over a putt for 45 seconds reading contours. Read the book while others are putting so you already know your line when it's your turn.

A junior who uses a yardage book slowly is worse off than one who doesn't use it at all. Pace of play matters. If the book is adding time, put it away.

Yardage books are permitted under the Rules of Golf. You can carry one, consult one, and mark one during a round.

Green-reading books are a newer and more complicated question. The USGA and R&A have introduced restrictions on highly detailed green-reading books — specifically those that show slope direction and gradient in a way that goes beyond what a player could observe themselves. Some tours have adopted these restrictions; others haven't yet.

The practical rule: check the local rules sheet at every event. It will specify what's allowed. When in doubt, ask the rules official before the round — not during it.

At most junior tournament levels currently, a standard green book with contour lines is permitted. But this is an area where rules are evolving, so always verify.