Form 1 NATIONAL RAILROAD ADJUSTMENT BOARD Award No. 29437
 THIRD DIVISION Docket No. MW-29602
 92-3-90-3-577
 The Third Division consisted of the regular members and in
 addition Referee Dana E. Eischen when award was rendered.

 (Brotherhood of Maintenance of Way Employes PARTIES TO DISPUTE: (Consolidated Rail Corporation

(1) The Agreement was violated when the Carrier failed and refused to afford Mr. G. V. Pfistner a seniority date on the Columbus Division B&B Inspector Seniority Rost date on the Columbus Division B&B Foreman Seniority Roster (System Docket MW-728).

 (2) The Carrier shall allow Mr. G. V. Pfistner a B&B inspector seniority date identical to his B&B foreman seniority date on the Columbus Division Seniority Roster."

 FINDINGS:
The Third Division of the Adjustment Board, upon the whole record and all the evidence, finds that:

 The carrier or carriers and the employe or employes involved in this dispute are respectively carrier and employes within the meaning of the Railway Labor Act as approved June 21, 1934.

 This Division of the Adjustment Board has jurisdiction over the dispute involved herein.

 Parties to said dispute waived right of appearance at hearing thereon.

 Claimant has established and holds seniority as a Bridge and Building (B&B) Helper and Mechanic dating from June 19, 1978 and November 1, 1978 respectively. As of December 3, 1984, Claimant was awarded a position of B&B Foreman on the Columbus Seniority District, however, he was not shown on subsequent rosters. Bridge and Building Columbus Seniority District Roster, and further protested the omission of his name from the Columbus Seniority District Roster for Inspectors.

 On October 25, 1989, the Manager of Labor Relations informed the Claimant that his name would be added to the Columbus District B&B Roster in the classes of B&B Foreman and B&B Assistant Foreman with a seniority date of
 Form 1 Award No. 29437
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 December 3, 1984. However, the Carrier advised the Claimant that there was no basis for granting him seniority as an Inspector by virtue of being awarded the Foreman position.

 Claimant and the organization objected, pointing out that historically and by long-standing prac positions simultaneously were placed on the B&B rosters with the same date on the B&B Foreman, B&B Assistant Foreman, B&B Mechanic, B&B Helper and B&B Inspect although Carrier concedes that some managers continued to adhere to the old practice under the new rule.

 For its part, the Organization maintains the Carrier's contention that Rule 4, Section 1(a) specifically prohibits the parties' practice of placing the names of emplo Columbus Division Roster were listed on the same dates that they had established seniority as B& which have been historically applied by the parties.

 It is the Carrier's contention that under the former Pennsylvania Railroad BMWE Agreement effective December 16, 1945, Inspectors in the B&B Department were a separate class within the Bridge and Building Department roster. However, Carrier asserts that the 1982 Agreement set up a distinct category of Inspector, and therefore Inspector is no longer considered a class within the Foreman category. According to the Carrier, if a B&B Helper secures an appointment to dates as an Assistant Foreman and a BSB mechanic, but is no longer eligible to secure the date as an Inspector. Carrier concedes that from February 1, 1982 to November 14, 1983, employees obtaining B&B Foreman positions were "erroneously" granted Inspe contract provisions."

 It is well-known that this Carrier was formed by an act of Congress from a group of bankrupt Eastern freight railroads. Among the former component railroads w apparently were carried forward essentially unchanged from the Penn Central /BMWE Agreement- However, the record does not contain the seniority rule and seniority roster language from the old Penn Central contract; indeed, no citation or reference to th evidence does indicate that Rules 1 and 4 of the Agreement now in dispute read, in pertinent part, as follows:
 Form 1 Award No. 29437
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          The seniority classes and primary duties of each class are:


              Bridge and Building Department


              A. Inspector Roster:


                  Inspector


                  Inspect bridges, buildings and other structures.


              A-1. Inspector Scale Roster:


                  Inspector Scale


                  Inspect scales.


              b. Bridge and Building Roster:


                1. B 6 B Foreman


                  Direct and work with employees assigned under his jurisdiction.


                2. Assistant Foreman


                  Direct and work with emloyees assigned to him under the supervision of a Foreman.


                3. B S B Mechanic


                  Construct, repair and maintain bridges, buildings and other structures.


                4. B 6 B Helper


                  Assist B &B B Mechanic."


                      "RULE 4 - SENIORITY


          Section 1. Seniority date.


          (a) Except as provided in Rule 3, Section 5, seniority begins at the time the employee's pay starts. If two (2) or more employees start to work

Form 1 Award No. 29437
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 92-3-90-3-577
 on the same day, their seniority rank on the roster
 will be in alphabetical order. An employee as
 signed to a position of higher class than trackman
 will begin to earn seniority in such higher class
 ' and lower class on the same seniority roster in
 which he has not previously acquired seniority from
 the date first awarded an advertised position in
 such higher class. He will retain and accumulate
 seniority in the lower class from which assigned.
 An employee entering service in a class above that
 - of trackman will acquire seniority in that class
 from the date assigned to an advertised position
 and will establish seniority as of the same date in
 all lower classes on the same seniority roster."
 The Organization made timely objection to Carrier's introduction of
 new evidence and argument for the first time in its submission to the Board,
 and we may not consider that de novo material. The following exchange sets
 forth the positions and evidence joined in handling on the property:

                  "Objection to Managers Denial


          This is a Roster Protest for the position of B&B Inspector on the Columbus, Ohio Seniority District.


          The claimant bid in a B&B Foreman Position but was not placed on the Roster. He protested the Roster and now as agreed to by all the parties he is being placed in his proper place on the Foreman Roster. The claimant has also asked that his name be placed on the B&B Inspectors Roster with the same date of his Foreman Seniority. Here is where the parties differ.


          On the Columbus Seniority District the practice is and has been up to now that when an employee is awarded a B6B Foremn position his name will be placed on the Foreman Roster and the Inspector Roster with the same date.


          Examples of this are H. J. Murdock, S.A. McDade, A. A. Craig, T.M. Gilbert, R. N. Williams, R.W. Smith, R.E. Prosser, J. K. Lafferty, L. Hackney, J.S. Gilbert, E.A. Sellers, J. D. Serio, W.F. Washmuth, M.T. Cohee, B.R. Campbell, R. L. Ritterbeck, R.M. Peery, E. G. Gallis, L. J. Sacher, and R. D. Alexander. Of the 25 Inspectors listed on the Roster 20 of them have the same date on the Foreman Roster. Four of

Form 1- Award No. 29437
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 92-3-90-3-577
 them do not have the same date because they bid an
 Inspectors position in first before bidding a Foreman
 job in. The Inspector pays less than the Foreman and
 that's why they were not put on the higher Foreman's
 Roster at the same time as they acquired their
 Inspector Date.
 We are asking that the claimants name be placed on
 the Inspectors Roster with the same date of his
 Foreman Seniority.
 Either we are right with our one date or they are
 all wrong with their 20 dates."
 "We disagree with your contention G. V. Pfistner
 should be given a B&B Inspectors date on the basis of
 alleged practice on the Columbus Division which
 purportedly allowed an employee awarded a B&B Foreman
 position to acquire seniority on the B&B Inspectors
 roster concurrently. You are cognizant the provi
 sions of Rule 4 Section 1(A) does not provide for
 obtaining senioriy in another class wihtout first
 being awarded a position in that class. Records show
 G. V. Pfistner never was awarded a B&B Inspector's
 position, thus he has no seniority in that class.
 In view of the foregoing, your roster protest is
 denied."

 Carrier points out that arbitration tribunals, including the Board, frequently have held that even a long-standing past practice must yield in the face of contrary language which is clear and unambiguous. See Third Division Awards 28034, 20711. However correct that principal might be in the abstract, its application requires a concrete factual showing of unambiguous language which admits of only one interpretation. In the particular set of facts set forth on this record it has no application. For many years prior to the 1982 Agreement, when the Carrier promoted an employee to B&B Foreman's position, the employee was also awarded seniority as a B&B Inspector. The language of Rule 1, as amended in 1982, might colorably be interpreted to vary that practice of applying Rule 4 but it is not crystal clear that the Parties Intended thereby to abandon the practice. Further, it is not disputed that this practice continued subsequent to 1982.

        In Third Division Award 2436 the Board held:


          "It is fundamental that a practice once established remains such unless specifically abrogated by the contract of the parties." See also Third Division Awards 5167 and 18548.


          See also Third Division Award 29057:

Form 1 Award No. 29437
 Page 6 Docket No. MW-29602
 92-3-90-3-577
 "One of the tools of interpreting ambiguous
 contract language is past practice. It is in
 dicative of what the Parties intended the language
 to mean and how it should apply."
 A W A R D

        Claim sustained.


                            NATIONAL RAILROAD ADJUSTMENT BOARD

                            By Order of Third Division


Attest: Qi

      Nanry J. -Executive Secretary


Dated at Chicago, Illinois, this 21st day of October 1992.