arch crown

• 拱顶

arch crown的用法和样例：

例句

1. Emission joints of arch and vault shall correspond to direction of radius.
   拱和拱顶的放射缝，应与半径方向相吻合。
2. A wooden frame built especially to support the sides of an arch until the keystoneis positioned.
   支拱板条专门用来在拱顶石放置好以前支撑拱的两边木架子。