TCD is a proprietary file format used by Technobox software applications for storing created CAD projects. Technobox was a German software released in 1990s; versions 4 through 6 supported TCD file format.

TCD 2D CAD project files are rarely used this days. In order to open a TCD file on a modern operating system a CAD file viewer tool called Tenado Viewer must be used. The tools is available for free, courtesy of Technobox GmbH.