50. ADVICE AND AIDS

1. ADVICE A player is not entitled to receive advice from anyone, except his partner in doubles play and, subject to Law 51(a), should not take advantage of unsolicited information or advice. However, if someone other than the adversary or a duly authorised referee informs:
1. a player that he has committed an error, and does so after the player has quitted the court believing that the requirements of Law 4(e)(1) have been met, the player must not declare the error.
2. the striker that he has committed an error, the striker must immediately declare the error if he believes the information or advice to be correct and the limit of claims has not passed.
3. the adversary that the striker has committed an error, the adversary must, subject to Law 23(b), immediately forestall play if he believes the information or advice to be correct and the limit of claims has not passed.
4. a player that an interference under Laws 30 or 31 has been committed, the player must immediately declare the interference if he believes the information or advice to be correct.
In Laws 50(a)(2), 50(a)(3) and 50(a)(4), once the error has been dealt with, Law 55 must be applied when necessary to restore the balance of the game as nearly as possible to its state before the unsolicited information or advice was given.
2. TECHNICAL ASSISTANCE The striker may not make use of technical assistance from any written or electronic source, or artificial aids such as coins to assist him in placing a ball for a stroke.
3. MARKERS No mark or marker may be made or placed inside or outside the court to assist the striker in gauging the strength or direction of a stroke or in placing a ball for a stroke, other than as follows:
1. the striker's mallet or that of his partner in doubles play may be used as a marker before the stroke starts;
2. the striker's partner in doubles play may act as a marker subject to Law 40(b); and
3. ball markers used to mark the position of a ball that must be temporarily removed or may have to be replaced.
4. TRIAL BALL During a game a ball must not be used as a trial ball for any purpose other than as part of the lawful positioning of a ball for a stroke or to permit the discharge of the duties of a referee.