12. For grooves with markedly varying separation (See Figure 6 below), the above procedures need modification, though the same measuring technique applies. In general, the concept of average groove pitch has to be abandoned and groove pitch (or separation) taken for individual pairs of adjacent grooves. In the sample illustrated, the club face would need to be divided into two or even three separation regions.
Difficult cases should be submitted to the The R&A or USGA for a ruling.
13. For used clubs with worn grooves the width measurements must be made on grooves which are not worn. These can nearly always be found near the toe of the club, or high on the face. Avoid the extreme end of the grooves since the width sometimes varies there. If it is impossible to find ten unworn grooves, measure as many as possible and make the necessary modifications to the calculation of average width.
If the grooves on a used club have been deliberately altered by filing or the use of a groove scoring tool, then the club should be treated as though it were new and the grooves measured near the centre of the face.
14. Very occasionally grooves will be found which are either very shallow, or have sides which make an angle of less than 30° to the horizontal. In these circumstances the marking tool will not work properly and the club should be submitted to The R&A or USGA for a ruling, although it may be possible to give an “on the spot” conforming ruling if the grooves clearly conform