Trapped Key Interlocking provides a simple solution to make Electrical Installations, Process Industries, Machines and most Industrial Processes SAFE for people by preventing unauthorised access and forcing implementation of sequence of operations in a predetermined order. The “mechanically trapped key” is released from its respective lock for transfer to another lock controlling an access door, machine or valve only when the primary drive or hazard has been isolated. Trapped Key Interlocking is a simple, but bobust solution to avoid loss of life and property due to human error.