It would have worked if he had known the code.

"If I may ask, how did you know the code to get in here?"

The message was understandable only to someone who knew the code.

Only he knew the code for the tiny series of computer buttons.

He couldn't know the code, she repeated to herself like a prayer.

"But of course I don't know the code, and you won't tell me."

There were only a few men who knew the secret code to use that channel.

Nonetheless, critics of the practice question how well the workers know the American code.

That it is a secret code known only to the initiated.

I guess they know the code for the door, then.