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Cricket Web: All-Time Legend
The theory behind it is that the ball is more likely to move with a higher/more pronounced seam and stitchesI try to sneak in a few feet /metres in rugby yes.
But I've never picked the seam in cricket or seen anyone in my team do it. I didn't know that was common.
Members of the fielding team would use a finger nail to lift part of the central seam or individual stitches
Nowadays, you have to give the ball to the umpire to get grass/dirt out of those areas as the excuse used to be that you were simply cleaning the ball