(Brotherhood of Railroad Signalmen
 PARTIES TO DISPUTE:
 (Southern Pacific Company (Pacific Lines)

(a) The Southern Pacific Company violated the current Signalmen's Agreement effective April 1, 1 it failed and/or declined to apply the Scope Rule, which resulted in the violation of Rule 70, by assigning the recognized signal work of constructing and installing a slide detector fence connected with the signal system in tunnel No. 20 at Auburn, California.

 (b) Messrs. E.P. Tankersly, Mr. R. N, McNamer, Mr. T. R. Johnson, Mr. J. E. Whitlock, Mr. D. L. Hicks, and "r. G. G. Shaw, be allowed eight (8) hours each at the time and one-half rate of their assigrmients, for each of the following dates: Ac.gust 29, 30, and 31, September 1, 2, and 6, 1966.

OPINION OF BOARD: The Organization contends that the Carrier violated Rule 70
 when it failed or declined to apply the Scope Rule of the
 Agreement between the parties and assigned to Maintenance of Way Forces the
 recognized signal work of constructing and installing a falling rock dotectoi
 connected with the signal system in 'funnel No. 20 at Auburn, California.

 The Carrier contends that all of the signal work in connection with the slide detector fence was in fact performed by signalmen except the work of forming and installing metal arches from which to suspend the falling rock detector device, which work was assigned to Maintenance of Wav forces.

 As a result of a fire which partially damaged Tunnel No. 20, there was a hazard of falling rock which necessitated the installation of the detector device

 When it became apparent to the Carrier that the method of attaching wires to the rock ceiling of the tunnel by means of clevises was unsafe, the Carrier decided to install me set in cement at the sides of the tunnel to support the wires of the detector syster

 The Carrier argues that all cantilever and signal bridges are in fact installed by Maintenance of Way forces rather than signalmen, and that the metal arch here is similar in function.
                    Docket Number SG-17582


The fact that the Carrier originally assigned the forming of the metal arches to signalmen is not such a grant of exclusivity as would bar a later assignment to other forces. It is not disputed that all insulators and wires comprising the detector system were in fact installed by signalmen.

 Finally, there is no express reference to the work in dispute in the Scope Rule. Where there is no express reference to the work in the Scope Rule, then the intent of the parties can only be ascertained by past practice, custom and usage on the property (see 18919 Dugan, 11526).

 The Organization has failed to prove that the work in question by practice, custom and usage has been done system-wide exclusively by signalmen.

 This Board finds that the Carrier properly apportioned the work involved in this dispute.

 FINDINGS: The Third Division of the Adjustment Board, after giving the parties
 to this dispute due notice of hearing thereon, and upon the whole
 record and all the evidence, finds and holds:

 That the Carrier and the Employes involved in this dispute are respectively Carrier and Employes within the meaning of the Railway Labor Act, as approved June 21, 1934;

 That this Division of the Adjustment Board has jurisdiction over the dispute involved herein; and

        That the Agreement was not violated.


                      A W A R D


        The Claim is dismissed.


                            NATIONAL RAILROAD ADJUSTMENT BOARD

                            By Order of Third Division


ATTEST: ~~l~l~ `I~ ~.
 Executive Secretary

        Dated at Chicago, Illinois, this 12th day of October 19'/3.