纲举目张的英文：
Once the key link is grasped, everything falls into place.

Once is no custom
一次不成例

Do it for this once.
就干这一次吧。

Gordon is at once modest and clever.(at once …and…既..又)
戈登既聪明又谦逊

We have a key for the door of the house and a key for starting the car.
我们有房间门的钥匙和发动汽车的钥匙。

I left the key in the lock.
我把钥匙留在锁上，忘了取下来。

He fished in the bag for the keys.
他在袋子里摸找钥匙。

open link cable
开口链环锚链

The strength of the chain is in the weakest link.
链子的承受力在于最薄弱的一环。

They forged the links with the Labor Party.
他们与工党建立了联系。