Spreads the load on the wood
A wide washer under the head and nut stops them sinking into the timber as the bolt is tightened and as the wood dries.

Bolts, Washers & Ground Rods
Washers for pole-line bolts spread the clamping force of each bolt head and nut over the wood, sourced in standard and specialty types spread the clamping force of each bolt head and nut over the wood. GV sources square flat, square curved, round flat and spring lock washers; the curved square washer seats on the round face of the pole. Specify type, size, hole and quantity.
At a glance
A wide washer under the head and nut stops them sinking into the timber as the bolt is tightened and as the wood dries.
Square flat washers sit on crossarms and flat faces, curved square washers on the pole, round washers on steel fittings, and spring lock washers under nuts that must not back off.
Square 2 1/4 x 2 1/4 to 4 x 4 in (57–102 mm), 3/16 or 1/4 in (5 or 6 mm) thick, 11/16 in holes for 5/8 in bolts and 13/16 in for 3/4 in bolts, hot dip galvanized to ASTM A153.
Also known as
Also called square washers in the US. Spanish-speaking crews call it arandela plana.
A washer goes under the bolt head and another under the nut. On the round face of the pole a curved square washer is used so it bears along its full width. A spring lock washer is added under the nut where the joint must hold against vibration.
Common applications
Every through bolt in a crossarm assembly takes a washer at each end. The square washer is sized to the bolt diameter.
Spool bolts carry lock washers and a round washer as part of their kit. The washers hold the insulator and nut in place.
Guy attachments and pole fittings bear on washers at the pole face. Curved washers keep the load even on the round surface.
Questions answered
Washers finish the joints in the crossarm, secondary spool, down-guy and attachment assemblies, under Machine / Square Headed Bolt, Hex Headed Bolt, Carriage Bolt and their nuts.
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