Here ya go...
There is no provision in USBC specifications that would not allow a
ball to have 5 holes for gripping purposes which would include a thumb
hole and four finger holes (two each drilled conventional and
fingertip). The equipment after drilling would have to meet all USBC
specifications for weight and balance to be used in certified
competition.
I hope this information is helpful in answer to your question.
Sincerely,
Mark Grubich
USBC Senior Rules Counselor
(800)514-BOWL Ext. 3354
mark.grubich@bowl.com
quote:
The rule further states that you must use every finger hole that is drilled. For instance, you can technically get DQ'ed for throwing your ball without your thumb in it, if you have a thumb hole drilled in the ball. Likewise, you have to have 2 fingers in the ball if there are 2 finger holes drilled (I found this one out from a buddy, as he used to throw at 10 pin with only 1 of his fingers in the ball plus his thumb...but someone gave him a warning at a tourney that he wasn't allowed to do that).
Big Willy Style
PS...too lazy to look up the exact reading on the rule, but I'm sure it's either in the drilling legality section, or where they got the rule you can't bowl "out of the norm...ie. between your legs).
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