Appendix II, 1b states that:
| All clubs may incorporate features for weight adjustment. Other forms of adjustability may also be permitted upon evaluation by The R&A. The following requirements apply to all permissible methods of adjustment:
(i) the adjustment cannot be readily made;
(ii) all adjustable parts are firmly fixed and there is no reasonable likelihood of them working loose during a round; and
(iii) all configurations of adjustment conform with the Rules.
During a stipulated round, the playing characteristics of a club must not be purposely changed by adjustment or by any other means (see Rule 4-2a).
In order to preserve the integrity of Rule 4-2a (Playing Characteristics Changed), this Rule clearly states that it must not be too easy for a player to make adjustments during the course of a stipulated round. This is interpreted to mean that adjustments must require the use of a special tool, such as an Allen key, a Phillips screwdriver or a custom made device. It must not be possible to make the adjustment just by using the fingers or some other object which would normally be kept in a golfer’s pocket, for example a coin or a pitch-mark repair tool.
The above restrictions have been included in the Rules in order to encourage the player to make all of the necessary adjustments to his clubs before starting his round, and to protect him from either unwittingly or purposely making adjustments during a round.
Fig. 1 - Adjustability for weight
(ii) Adjustability for Weight
All clubs may be designed to be adjustable for weight, provided the adjustment mechanism conforms to the conditions described above and in Appendix II,4b of the Rules. Examples of what would and would not be permitted are illustrated in Figure 1.
As already mentioned in Section 5 - General, as far as adjustments for weight areconcerned, the only exception to the conditions described in (i) above is the addition or removal of lead tape. This is a practice which pre-dates theintroduction of the adjustability Rules and is permitted on ‘traditional’ grounds. Of course, the addition, removal or alteration of lead tape during a round is not permitted (see Rule 4-2a and Decision 4-2/0.5 in "Decisions on the Rules of Golf").
(iii) Other Kinds of Adjustability
The 2008 edition of the Rules on adjustability were relaxed to allow all clubs to be designed to be adjustable in ways other than weight, including woods and irons. Manufacturers are encouraged, however, to submit all new adjustable design innovations for evaluation in the early stages of development.
All permissible methods of adjustment must require the use of a special tool, not just the fingers or a coin, etc. (see above). If, as is often the case, a screw is used to fix the mechanism, the club must, for all practicable purposes, be unusable without the screw being in place and tightly fixed. One exception to this “unusable” requirement is for a long putter with a shaft which dismantles into two shorter lengths for travel purposes. Here, a screw together (“pool cue”) joint is permitted with an Allen key screw, or similar, which penetrates the threaded section of the joint by at least half way. This combination potentially renders the putter usable even when the Allen key is not tightened, or is forgotten.
When assessing the conformity of an adjustable club, it is important to remember the third condition listed in Appendix II, 4b, and to check that it cannot be adjusted into a position which does not conform to the Rules. For example, a putter which is adjustable for lie must not be capable of being adjusted into a position where the shaft diverges from the vertical by less than 10 degrees (see Appendix II, 1d and Section 5 - Alignment), or any other position which would render the club non-conforming (see Figure 2).