Originally from Dispute Resolution Journal

Past practice is a difficult term to define. Since it may arise in conjunction with almost every operation in the plant, it becomes too broad to define in simple terms. It usually relates to some form of contractual relationship that has developed over time between an employer and its employees. In many cases, it is not formed by any concrete decision made by either side. Normally, a practice will originate at the lowest level of union and management. The rank and file and their immediate supervisors are often the parties who form these practices. The practices may include anything from how long a lunch break the employees take to how a certain job is done. The important thing is that many of these practices are "as necessary to the proper functioning of the plant as they are beneficial to the employees."

There is wide agreement among arbitrators in the acceptance of an operational definition of past practice. This is evident even from a cursory glance at arbitrators' comments on the subject. Arbitrator Clair V. Duff, for example, has said that "Past practice may be described as a pattern of conduct which has existed over an extended period of time and which has been known to the parties and has not been objected to."