under lock and key

idiom

: in a room, box, etc., that is locked

The jewels are kept under lock and key.

The prisoner is being kept/held under lock and key.

Examples of under lock and key in a Sentence

Recent Examples on the Web

But unlike in earlier eras, when embedding with a campaign at least provided reporters with regular access to the candidate, the contenders for second place largely remained under lock and key. —Kyle Paoletta, Harper's Magazine, 30 Mar. 2024

Penthouses and a rooftop remain under lock and key until later in 2024. —Cnt Editors, Condé Nast Traveler, 13 Dec. 2023

And, along with brazen retail thefts that have forced stores to keep common products under lock and key, the incessant porch-pirating has added new challenges to shopping. —Peter Hermann, Washington Post, 13 Apr. 2024

Those who auditioned didn’t use pages of the actual script, which remained under lock and key, but utilized scenes from other movies that required comparable skillsets, like rattling off complex equations. —Zoe Hewitt, Variety, 15 Dec. 2023