30 Symmetry System (30 대칭 시스템)Always hit 30, arrive at the symmetric point

A very simple Korean system: if the cue ball is sent from where it lies to the 30 point of the opposite long cushion (aim 30 in Diamond System numbering, the 3rd diamond from the far corner) with 2 tips of spin at 1:30, it goes around the short cushion and the long cushion it started from and arrives on the opposite long cushion at the point symmetric to the start about the long axis of the table. No calculation is needed; only if the arrival differs from the symmetric point is the aim shifted in half-diamond steps. It is used as a base line in bricole shots and in 뒤돌리기 (taking ball 2 from behind and going around) and 옆돌리기 (taking ball 2 from the side and going around) positions.

When? When the cue ball is between 35 and 50 on the left long cushion in Diamond System start numbering (or between 60–90 on the top short cushion), and ball 3 is waiting near the point symmetric to the start. As the start number rises (60 and above) it becomes harder to shorten the arrival; in this zone the system is used more for lengthening.