In order to judge the depth of a groove on a club, the disc should be placed onto the face with the ridge running along the inside of the groove. The user should then apply pressure to the disc, on both sides of the ridge, to see if the disc will rock from side to side.
If the disc does noticeably rock, then the groove cannot be too deep. It means that the depth of the ridge is greater that the depth of the groove.
If, on the other hand, the disc lies flush with the face and cannot be rocked, it means that the groove is likely to be too deep.
In both instances above, the gauge should be used on at least six grooves within the “impact area” of the face (or near the toe for club faces which are quite worn).
If 50% or more of the grooves tested appear to be too deep when using this gauge, the club should not be carried