Under Lock and Key — Meaning, Usage & Examples

What it means...

Kept very securely, locked away and protected.

When something is under lock and key, it is stored somewhere only certain people can access.

It applies to physical objects as well as sensitive information.

Use it when…

When confidential documents are stored securely and restricted
When a valuable item is kept in a safe or protected location
When someone guards a secret very carefully

Don’t confuse with...

"Hush-hush"

—

Something kept quiet as a secret, not necessarily locked away

"Close to Your Chest"

—

Keeping information private and guarded, not physically secured

"Under Lock and Key"

—

Physically or figuratively locked away and tightly secured from others

Where you’ll hear it

You’ll hear the "Under Lock and Key" idiom in real life — at work, in relationships, or in the media.

Work & Business

Corporate Issues

The merger documents were kept under lock and key until the official announcement was made.

Relationships & Social Life

Family

Their grandmother kept every family heirloom under lock and key.

Media & Everyday Life

News

The evidence was kept under lock and key pending the outcome of the investigation.

‹›

Use it like this

Here’s how to use "Under Lock and Key" idiom naturally in real conversations, with real examples.

Work & Business

Office Conversations

Boss

Where are the prototype files right now?

You

Under lock and key in the secure server — only you and I have access.

Relationships

Talking to friend

Friend

Did you tell anyone about the surprise party?

You

Not a soul — I've kept it under lock and key.

Everyday Conversations

Everyday problems

Friend

My passport keeps going missing around the house.

You

Keep it under lock and key — get yourself a small safe.

‹›

Last updated:

April 20, 2026

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