Appendix II, 4d states that:
| The clubhead must have only one striking face, except that a putter may have two such faces if their characteristics are the same, and they are opposite each other.
The exception for putters was introduced in order to accommodate traditional blade-type putters.
Determining whether a surface constitutes a second (or third) striking face is often a matter of opinion. However, in general, a surface should be considered an additional striking face if:
• the area is flat and it is clearly designed to be used for striking the ball; or
• it is opposite the intended face and consists of a flat surface of a different loft and/or material; or
• it is a flat surface on the toe and/or heel of a cylindrical, rectangular or square head design which could effectively be used to strike the ball; or
• it could otherwise effectively be used to strike the ball.
All three of the putters illustrated in Figure 33 would be ruled non-conforming.
The addition of lead tape to the secondary face of a two-faced putter would not be contrary to the Rules. In addition, cosmetic or decorative markings on one of two permissible surfaces, that do not affect the performance, will not usually create a different striking face in breach of this Rule.