Lock Out, Tag Out, is a safety procedure used in industrial settings to ensure that dangerous machines are properly shut off and not able to be started up again prior to the completion of maintenance or repair work. LOTO is safety procedure mandated to prevent the accidental startup of a machine, valve, electrical panel, etc while it is in a hazardous state and being worked on by a worker.  The unit must be isolated and identified by an obvious tag or device as being inoperative until such time it is safe to operate the unit and the identification is removed by the worker.