Noun
crossarm (plural crossarms)
The horizontal member of a cross-shaped object, such as the horizontal bar of power poles or telephone poles.
However, for high voltage transmission lines, strings of cap-and-pin (suspension) insulators are used, attached to the crossarm in a horizontal direction. Source: Internet
These pieces of glass were positioned on a tapered wooden pin, vertically extending upwards from the pole's crossarm (commonly only two insulators to a pole and maybe one on top of the pole itself). Source: Internet