A two (2) hour guarantee applies whenever an operator or mechanic is required to return to work during the evening meal break (1800 to 1900 hours) or midnight meal break (2400 to 0100 hours) after having worked a full eight (8) hour shift. If two hours work is not available, each operator or mechanic so affected will be released from work and charged based on the straight time rate for the number of hours necessary to complete the two hour guarantee.