“关”，要塞也；《周利》注说是“界上之门”。无论怎样，“关”的位置大概很重要。所以，自古兵家就有守关、攻关、过关之说。守关难。守关是据险以拒敌。杨六郎的重要职责就是把守三关口，守住三关，即可拒故于国门之外。古代战争中有许多争夺关隘的实例。为夺关胜敌，甚至 “Off”, fortress also; “Zhou Li” note that “the door to the world.” In any case, the location of “off” is probably very important. Therefore, the ancient military strategist has Shouguan, research, clearance said. Keep customs clearance difficult. Customs clearance is based on danger to resist the enemy. Yang Rokuro’s important duty is to guard the three pass, keep the three points, you can refuse to be out of the country outside. There are many examples of contention for pass in ancient wars. To win the victories, even