This is the key to the lock.

这是这把锁的钥匙。

youdao

Give away any food you have on hand, or lock it up and give the key to the neighbours.

把你手头的食物分发送人，或锁藏起来，把钥匙交给邻居们。

《柯林斯英汉双解大词典》

Shine the torch on the lock while I try to get the key in.

我插钥匙时，请用手电筒照着锁头。

《牛津词典》

The only fix is to keep everything BACK in the datacenter, or under lock and key when delivered out to their laptops.

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At the same time, Lenovo didn't have to shrink down the Enter, Shift or Caps Lock key to compensate.

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The former partners tried to keep Cawley's new claims under lock and key at the courthouse.

FORBES: Magazine Article