RULE 87. VACANCIES POOL FREIGHT SERVICE.  (a) Permanent vacancies in pool freight service will not be bulletined, but will be filled promptly by assigning the senior engineer having a written application on file with the crew dispatcher at the time the vacancies occur.  

(b) When a pool freight engineer is absent from his assignment for more than 15 days for reasons other than taking his vacation, his vacancy will be promptly filled from applications as provided in Section (a).

(c) Should a regular turn in pool freight service be vacated under provisions of Rule 85, it will be promptly filled from applications as per Section (a).  

(d) Engineers assigned in pool freight service will not be permitted to vacate their turn and take another in the same pool.