Can I clean, sand or put rosin on my ball during league play?

Not once competition starts. Competition starts when any bowler throws a ball for score.

• Before league play: you may sand, polish or clean any ball.
• During league play: you can't alter the surface of any ball, including spares in your bag that you haven't used yet. No abrasives, polish or cleaner, and no patting the ball with rosin or powder (wiping it off afterward doesn't make it legal). Rosin or powder on your hand is fine as long as it doesn't leave residue on the ball.
• Practice: you may use an approved cleaner during practice unless league rules say otherwise.
• Residue you can't wipe off with a dry towel: ask a league officer for permission, then you may clean the whole ball with an approved cleaner.

Penalty: if you didn't know the rule, the ball is removed from competition. If you did know, the ball is removed and the games are subject to forfeiture. Refusing to remove the ball also makes the games subject to forfeiture.

Other ball rules: maximum weight 16.00 lb (no minimum); house balls are allowed. From January 1, 2027, identification markings (brand/logo, ball name, serial number) may not be re-engraved, and balls with re-engraved or unreadable serial numbers aren't allowed in certified competition.