It Pays to Know the USGA Equipment Rules

4. Clubhead

a. Plain in Shape

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. It is not practicable to define plain in shape precisely and comprehensively. However, features which 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);
• facsimiles of golf balls or actual golf balls incorporated into the head;
• 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.

(ii) Woods and Irons

• 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.

Examples of features not permitted under the “Plain in Shape” Rules and guidelines for putters include the following:

    * Appendages for the purpose of meeting dimensional specifications — see Figure 22;
    * Features of any nature that extend above the top line of the face by more than 0.25 inches (6.35 mm);
    * Holes through the face — see Figure 23;
    * Facsimiles of golf balls or actual balls incorporated into the head — see Figure 24;
    * Heads designed to resemble other objects (i.e., bottles, cars, vegetables, body parts, etc., — see Figure 25);
    * Optical devices such as prisms, mirrors, reflective materials, etc. — see Figure 26;
    * Electronic devices such as light beams and metronomes, or mechanical devices such as spirit levels, etc. — see Figure 27.