Eight criteria are examined in ruling on past-practice grievances:
1. Does the practice concern a major condition of employment?
2. Was it established unilaterally?
3. Was it administered unilaterally?
4. Did either party seek to incorporate it into the body of the written
agreement?
5. What is the frequency of repetition of the practice?
6. Is the practice of long standing?
7. Is it specific and detailed?
8. Do the employees rely on it?