False bottom

A false bottom is an internal partition in a container, typically at the bottom of a drawer, suitcase or similar item, enabling the concealment of objects from a cursory examination of the item's contents. A false bottom may be present if the internal dimensions

Dimensions

Dimensions is a French project that makes educational movies about mathematics, focusing on spatial geometry. It uses POV-Ray to render some of the animations, and the films are release under a Creative Commons licence....

 of a container do not match its external dimensions after taking into account the thicknesses of constituent materials and structures used to build the object.