Many labor agreements specify the duties that may be performed only by individuals in certain jobs. Management violates this contract if the duties are assigned to persons in other jobs or if members of management perform them. It is obvious that the other workers were aware of this provision in the labor agreement. A supervisor such as Marcus Ned would not be authorized to put gasoline in a cherry picker. Not even the operator could do that, only the oiler whose job itwould be to keep the machine gassed and oiled and in good working order