【壁垒森严】〖bì li sn yán〗[strong defense preparations; a well-organized institute; strongly fortified; an unassailable stronghold]

壁耳墙风谍奸肃，

垒壕工事金汤固。

森然界限分明划，

严密城防龙盘踞。

军事戒备严密。比喻彼此界限划得很分明。Military guard tight. Describe each other boundaries drawn very clear.同：严阵以待、固若金汤。反：不堪一击、一触即溃。