i just want to share the experience with the others ja.... um.....i know..sometimes...when there is other ball blocking the potting line towards the pocket....then need to use "west" to make the object to have compact more than 1 "cool" to go to the pocket..... actually...it's useless....for expert.....they will avoid using dup ball....but i am only a begginer..
i will choose to dup just 1 'cool' to pot my object ball when my potting line is blocked because the object ball rebounded has '反西' when i am powerful to dup it以我所知