《宋史·志·卷三》
左星是南星，是用来守备关隘桥梁而抵抗发难的，在险阻的地方设置守备，是懂得谋略的证明。
左星，南星也，所以备关梁而拒难也，设守险阻，知谋徵也。
The left star is the south star, which is used to guard the passes and bridges and resist attacks. Setting up defenses in inaccessible places is a proof of understanding strategy.