A Guide to the Rules on Clubs and Balls

Plain in Shape

The "plain in shape" requirement in Appendix II, 4a originates from the ‘traditional and customary’ requirement in Appendix II, 1a. It is purely a descriptive rule, although in reality it can be challenging to define exactly what a golf club can or should look like. The following section should go some way towards explaining and illustrating what is and what is not permitted.

The essence of the Rule is encapsulated in the first three sentences:

 The clubhead must be generally plain in shape. All parts must be rigid, structural in nature and functional. The clubhead or its parts must not be designed to resemble any other object.

This basically means that the design of the clubhead must have the general appearance of a golf clubhead as opposed to another object and must not incorporate features which are designed to resemble another object (see Figure 16). All parts of the head (including permanent, permissible appendages) must be rigid throughout their length – i.e. it must not be possible to bend or flex them by hand. (see Figure 17).

Fig. 16 - Facsimiles of other objects

Fig 16

Fig. 17


The next section of the Rule freely acknowledges that it is not easy to fully define what is "plain in shape". However, in an attempt to better clarify the Rule and its interpretation, the 2008 edition of the Rule was split into two categories – one which covers "all clubs" and the other which covers the additional specifications relevant only to "irons and woods". The Rule reflects the more liberalised position for putters which has evolved over the years and it is deliberately more detailed as to what is and what is not permitted for irons and woods. However, it should be remembered that these are not exhaustive or all inclusive lists. Even if a club satisfies all of the points outlined below, there may still be features or characteristics which render it not "plain in shape". An overall assessment of the appearance of the head should always be made.


(i) All Clubs

The specifications for "all clubs" are as follows:

 It is not practicable to define plain in shape precisely and comprehensively. However, features that are deemed to be in breach of this requirement and are therefore not permitted include, but are not limited to:
(i) All Clubs
• holes through the face;
• holes through the head (some exceptions may be made for putters and cavity back irons);
• features that are for the purpose of meeting dimensional specifications;
• features that extend into or ahead of the face;
• features that extend significantly above the top line of the head;
• furrows in or runners on the head that extend into the face (some exceptions may be made for putters); and
• optical or electronic devices.

To take each of these clauses in turn:

Holes through the Face:

Holes through the face are not permitted – see Figure 18.

Fig. 18

Holes through the Head:

• Holes through the head are not permitted for wood heads – see Figure 19.

• Holes through the head are not permitted for iron heads. However, features within the cavity back of an iron clubhead that form a hole or holes may be permitted, (e.g. support bars), provided that the feature is contained within the outline of the main body of the head and the hole cannot be viewed from above. In addition, the feature must not be designed to affect the performance of the club – see Figure 20 a/b.

Fig. 19                                         

Fig. 20


• This clause is interpreted very liberally for putters and holes through the head (excluding the face) for any purpose including aiming, sighting or alignment are permitted – see Figure 21 for examples.

Fig. 21

Features for the purpose of meeting Dimensional Specifications:

Appendix II, 4b requires that, for all clubs, the distance from the heel to the toe of the clubhead is greater than the distance from the front to the back (see below). Clubs which incorporate features which are designed to or have the effect of circumventing this requirement are not permitted – see Figure 22.

Fig. 22 - Feature at toe deemed to be for the purpose of meeting dimentional specifications. It would not be considered to be part of the face (non-conforming).

Features that extend into or ahead of the face:

• Permitted features in or on the main body of the head must not extend into the face of an iron or wood club. This would include alignment features on the crown – see Figure 23. Alignment lines which have been engraved or inscribed onto an iron clubhead would generally be permitted.

Fig. 23

• Certain features are permitted to extend into the face of a putter, including alignment features and concavities (or furrows) on the crown (see Section below on Furrows and Runners). However, such features must not have a depth or height greater than 0.25 inches (6.35mm) when measured against the top line of the face.

• Features of any nature that extend ahead of the face are not permitted on any club – see Figure 24.

 Fig. 24                                                    Fig. 25



Features above the top line of the head:

• For putters, alignment or other features must not extend above the top line of the face by more than 0.25 inches (6.35mm) – see Figure 25.

• For woods and irons, features which otherwise meet the requirements for "plain in shape" must not extend above the top line of the head by more than 0.1 inch (2.54mm).

• Permanent or semi-permanent lines or other markings which have been painted, inscribed or otherwise incorporated (see Section 5-General(iv)) for alignment purposes are permitted.


Furrows and Runners:

• Furrows or runners which extend into the face of a wood or iron club from any part of the head are not permitted – see Figure 26.

Fig. 26

• Whilst this Rule is applied strictly for furrows or runners which may appear on the sole of a putter, exceptions may be made for other parts of the head – see Figure 27.

Fig. 27

Furrows and/or runners are deemed to extend into the face if the edge of the face has any concavity (point of inflection or turning point). This is determined by placing a straight edge along the edge of the face.

If a runner has been chamfered back away from the face, by at least 45 degrees, then it would not be considered to extend into the face – see Figure 28.

Fig. 28a - Putter with runners at the heel and toe

Fig 28a

Fig. 28b - Putter with chamfered runners at the heel and toe
Fig 28b

Optical and Electrical Devices:

Clubheads which incorporate prisms, mirrors, reflective materials, light beams, metronomes or mechanical devices such as spirit levels are notpermitted – see Figures 29 and 30.

Fig. 29 - Optical Devices                                  

 Fig.30 - Electrical and mechanical devices
Electronic devices in or on the club shaft or grip, which have the sole purpose of identifying the club, may be permitted. The identification information is restricted to:

            (a) the club’s owner, such as address and phone number;

            (b) inventory tracking information;

            (c) detection of the club’s use during a round.

Any such device must meet all other Rules and associated guidelines and must not vibrate or emit light or sound. If the device is capable of any function other than identification, the golf club will be considered not traditional and customary in form and make (see Section 5 - General) and, therefore, non-conforming.

Note: Any system used in conjunction with a club incorporating such a device must comply with the Local Rule Permitting the Use of Distance Measuring Devices (see Note to Rule 14-3 of the Rules of Golf and Appendix I, Part B, Section 9) and The R&A – USGA Joint Statement on Electronic Devices.

(ii) Woods and Irons

The additional specifications for "woods and irons" are as follows:

• all features listed in (i) above;
• cavities in the outline of the heel and/or the toe of the head that can be viewed from above;
• severe or multiple cavities in the outline of the back of the head that can be viewed from above;
• transparent material added to the head with the intention of rendering conforming a feature that is not otherwise permitted; and
• features that extend beyond the outline of the head when viewed from above.

In essence, the purpose of these additional requirements is to help preserve the traditional shape of such clubheads when viewed from above. The "plain in shape" Rules for woods and irons are less focused on sole features or other features which cannot be viewed from above. To go through each of these clauses in turn:

“Viewed from above”

“Viewed from above” is interpreted to mean the range from directly above the head to the normal address position.


• The restriction on cavities at the heel and the toe of the head does not prevent cavities around the skirt of the head, which may sometimes be viewed from above (see Figure 31a).

• Severe cavities (as viewed at address), which go all the way through the head, are not permitted. A “severe” concavity is one where the entrance to the cavity is narrower than its width at any other point (see Figure 31c).

• A single cavity in the back of the head is permitted (see Figure 31b) – but multiple cavities are not (see Figure 31d).

• Cavities in the crown of the head are permitted, even if they are designed primarily as an aid to sighting, aiming or aligning the swing plane or the head position, or to accommodate markings for such aids. However, all cavities on the crown are “filled” for the purpose of measuring the volume of the head (see Section 7b(i) below). See Figure 31 for examples of permitted and prohibited cavities.

Fig. 31

Transparent Material:

• Clubheads made entirely of transparent material are permitted.

• Transparent material that is added to an otherwise non-plain head does not render the head "plain in shape". For example, a wood head which has a vertical hole from the top surface through to the sole would be ruled non-conforming (see Section above and Figure 19). Filling this hole with a transparent material (e.g. perspex or glass), would not alter this ruling.

Features extending beyond the outline of the Head:

Any fin, knob, appendage or plate which is protruding beyond the outline of the head is not permitted, whatever the purpose.
NOTE: Whilst this provision does not apply to putters, The R&A has determined that unusual features which protrude beyond the outline of the toe or heel of a putter head may be ruled not "plain in shape" or not "traditional and customary".