Crossarms

Crossarms are horizontal structural members attached to a vertical support, projecting perpendicular to its axis, and used to carry or support loads or devices. The term is widely used in electrical, architectural, and other technical contexts. In power distribution, crossarms are mounted on utility poles to support lines and insulators. They may be single or multiple, with insulators attached at the ends or at mounting points along the arm. The arm length and configuration depend on voltage class, span, and local standards. Materials include wood, steel, and fiber-reinforced polymer; wood crossarms are often treated to resist decay, while steel and FRP crossarms may incorporate corrosion protection and ballast.

Three-arm configurations or bracketed arrangements enable three-phase wiring; crossarms may be reinforced with braces or hardware to withstand wind and vehicle impact. Modern crossarms can be designed to fail safely in a collision by breaking away or using sacrificial components.

In flagpoles and vessel rigging, a crossarm refers to a horizontal bar used to display flags or support sails on a yard. In architectural and church planning, crossarms describe the arms of a cross-shaped floor plan, notably transepts that extend from the nave to form a Latin or Greek cross.

Maintenance and safety considerations include inspecting for wood rot, insect damage, cracks, and fastener integrity, and replacing compromised arms. Regular checks are important in harsh climates or where load demands are high.

See also: utility pole, insulator, flagpole, transept, yardarm, cross-bracing.