locking stone

例句：

1. 1.The locking stone was used to secure the door.
   锁石被用来固定门。
2. 2.The locking stone is a valuable mineral resource.
   锁石是一种宝贵的矿物资源。
3. 3. The locking stone has been used for centuries in ancient architecture.
   锁石在古代建筑中被使用了好几个世纪。