dead letter box
dead letter drop

I take messages and leave them in a dead letter box.

This took him to continental Europe, where he may have recruited other agents and set up dead letter boxes.

"What if I don't make the dead letter box?"

She wished it even more after she dropped the message in the dead letter box, for there was one waiting to be collected.

"Nick, I need to finalize some drop off' she corrected herself "dead letter box details with you for the information and money exchange.

And why the dead letter box?"

'That'll be the DLB [dead letter box], yeah?'

Instead I put in an OP (observation post) on Sniper Two's dead letter box, which was just outside the market town of Thetford in Norfolk.

Paul Barrere - vocals and slide guitar on "Paradise", "Listen to the Wind", and "Dead Letter Box"

A dead drop or dead letter box is a method of espionage tradecraft used to pass items between two individuals using a secret location and thus does not require them to meet directly.

Steve Fister - rhythm guitar on "Paradise", "Trust Somebody", "Outside", "Daddy's Lil' Girl", "Dead Letter Box", and "Sweden", guitars on "Who You Are"

Doyle Bramhall II - lead guitar on "Trust Somebody", "Daddy's Lil' Girl", and "Dead Letter Box", rhythm guitar on "Daddy's Lil' Girl"

I'd put everything these snipers needed to know where to be, how to get there, what to do once in position, and, more importantly for them, how to get away afterwards with the weapons and equipment in their individual DLBs (dead letter boxes).

Tradecraft included stealing and photographing documents, code-names, contacts, targets, and dead letter boxes, and working as a "friend of the cause" or agents provocateur, who would infiltrate the target group to sow dissension, influence policy, and arrange kidnappings and assassinations.

The museum includes a replica underground Operational Base, as well as photographs, special weapons such as time pencil fuses and other explosives, dead letter boxes, agent instruction papers, and information about the special radio communications network installed by the Royal Corps of Signals.

After giving the cab driver a new drop-off point, I bought myself a blue ski jacket on Oxford Street, and went to a drugstore for some bits and pieces I'd need for the DLB (dead letter box), so I could leave our details with Liv.

Effectively, he had just inserted a dead letter drop into the Bendix Schere computer network.

Reports were to be collected from dead letter drops and relayed by radio operators of the Royal Signals from secret locations.

Dead Letter Drop (1981)

They had been trained to identify vehicles, high-ranking officers and military units, and were to gather intelligence and leave reports in dead letter drops.

Even though almost two petabits had been used when the agent-in-place passed it to him via a dead letter drop on a park bench, it was outrageously valuable to Martin.