The Cage is an easy to use 3D grid. Built into a 3D modeler, it provides a visualized reference coordinate system that helps the user to orient himself in 3D space, and that supports efficient alignment and snapping methods. It can be adapted with a single mouse click to any new viewing situation and reference system. The Cage was implemented in C++ under Open Inventor on Silicon Graphics workstations. It was tested as a part of a 3D authoring tool for virtual TV studios.