General Order 95
Definitions of Terms as Used in The Rules of This Order
21.0 Crossarm or Arm means a horizontal support attached to poles or structures generally at right angles to the conductor supported.
A. Combination Arm means a crossarm supporting supply conductors of 0 - 750 volts and supply conductors of 750 - 7,500 volts.
B. Related Buck Arm means a crossarm used to change the direction of all or a part of the conductors on the line arm immediately above or below. A buck arm is generally placed at right angles to the line arm.
C. Clearance Arm means a crossarm supporting conductors installed on a pole of another line for the purpose of maintaining the prescribed clearances of this order which, if the other line did not exist, could be maintained without such clearance arm.
D. Guard Arm means a crossarm installed on a pole not more than 4 inches directly above and approximately parallel to the messenger, cable or conductors being guarded. Guard arms shall not be used to support conductors, antennas, or other line facilities except as specifically provided in these rules (see Rules 84.8-B2c and 87.7-B).