To be very likely to succeed; to have success within one's grasp. This idiom refers to ancient contracts written on bamboo slips that were split into two halves; the creditor held the left half, or [[左券|左券|zuo3 quan4]], as proof of the debt.

To be sure of winning or achieving an aim; to have full assurance of success. In ancient times, a contract was split into two halves and the left half was held by the creditor as proof of debt.