The point on a pool table that is at the intersection of the head string and the long string.
While many players of eight ball place the cue ball here for the breaking shot, it is neither necessary nor effective.
However, this placement of the cue ball for the opening break of nine ball is quite effective. A strong hit, straight on the diamond, generally results in the forward triangle of six balls pushing back on the rear triangle of three, the two outside balls (those in line with the center ball) move towards the corner pockets, often one of them will sink.
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