The term "buckarm" is still used among lineworkers and refers to an identical crossarm on each side of the pole. Such construction typically was used for dead-ending open wire (among telephone, electric, telegraph companies, fire alarm, etc) as well for some reinforcement where the wires made a bend around a corner. Other installations include where weighty utility apparatus was added to a crossarm such as a transformer, junction box, etc., etc.

Each crossarm was (is) separated by and held in position via a through bolt affixed through the ends of both crossarms. In the early days a block of wood with a hole through its middle (with the through-bolt within it) was sometimes included to keep both arms equally and properly spaced. You can see such an instance on the lower crossarm, towards its far right. The upper crossarm also looks like it had the same type of wooden "spacer" with its through-bolt..