Concealment devices or diversion safes are used to hide things for the purpose of secrecy or security. They are made from an ordinary object such as a book, a candle, a can, or something as small as a coin. The idea is that such an inconspicuous object would not be expected to contain anything of worth.

Examples in espionage include dead drop spikes for transferring items to other people, and hollowed-out coins or teeth for concealing suicide pills. Examples in smuggling include suitcases with false bottoms for hiding contraband.

During World War II, a British organization called MI9 was responsible for creating many concealment devices for "escape aids" to assist prisoners of war to escape.