a strong wall

• 坚实的墙壁

a strong wall的用法和样例：

例句

1. They braced the sagging wall with a piece of wood.
   他们用一根木头撑住那堵往一边倾斜的墙壁。
2. On the back wall is our class News Bulletin Board.
   我们的班级新闻公告板在后面的墙壁上。